#medieval helmets

So, what makes a helmet good? Well, every helmet designed for pre-gunpowder-supremacy armed combat has one basic function it needs to do at a bare minimum: keep your brain inside your head and the enemy’s weapons outside it. Many helmets do more, but basically all of them, at a bare minimum, are designed to prevent the enemy’s weapons from smashing your skull in, slicing it open, or punching holes through it. The human skull is decently strong, especially the frontal bone, but it’s not strong enough to withstand a solid hit from a sword, axe, club, spear, arrow, mace, and so on. Getting hit in the head in armed combat, without a helmet, can kill you or inflict horrific, disabling injuries very, very easily.

(I’m using gunpowder supremacy here instead of gunpowder in general because there was a pretty long period where guns coexisted with armor and with muscle powered weapons being used as primary weapons, and a lot of “medieval” plate armor is actually from this period. As guns got better armor, and even helmets, gradually became less prevalent. The later reintroduction of helmets in the 20th and 21st centuries is a different scenario, because modern combat helmets are mostly meant to protect against shrapnel and usually aren’t expected to allow you to survive a direct hit to the head with the primary weapons carried by enemy soldiers)

Aside from protecting your brain case, there are a few other functions that a helmet may or may not be designed for.

1: Protect your face. Getting shot or stabbed in the face is still very likely to kill you. An arrow, or sword point, or spearhead can puncture your skull through your eyes or sinuses, and while other hits to the face may be varying degrees of survivable, getting your sinuses or jawbone smashed into pieces or cut in half is still life threatening, and severely disabling and/or disfiguring even if you live. Therefore, a helmet that keeps weapons from hitting you in the face is nice to have, especially if you’re facing projectile weapons and don’t have a large shield.

2: Protect your neck. Having your head intact is most useful if it’s also still attached to your body. Your neck is also full of vital stuff like the jugular veins, the carotid arteries, the trachea, and the spinal cord, so cuts, puncture wounds, or blunt trauma to the throat can easily be fatal.

3: Minimize the risk of injuries like concussions and whiplash by deflecting weapons instead of transferring all the energy of a blow. Concussions and whiplash are better than dying, but they’re still not good for you, and can potentially get you killed if they impair your ability to defend yourself.

The most protective helmet possible would be one that completely encases your entire head and neck in steel plates, and is rigidly attached to your torso armor to minimize forced head movements and not transfer any of an impact’s energy through your neck. However, as with any engineering problem, there are tradeoffs. Cost and manufacturing complexity is one of them, but there are also practical concerns. Any helmet has to have at least some gaps in it to let the wearer see and breathe, and even so a full face helmet restricts the wearer’s vision quite a bit and has limited ventilation, which means you’ll tire faster. Depending on the circumstances muffled hearing can also be a problem, and if you’re wearing the helmet all day then if you can’t eat and drink with it on you’ll have to take it off to do so. Finally, if the helmet’s attached to your torso armor it restricts moving your head, which can also make any vision restrictions worse because it’s harder to move your head so the vision holes in your helmet line up with something, but if your head and neck have to support its weight then a heavier helmet is more tiring to wear for long periods.

Now let’s get into the anatomical differences. Most military helmets throughout history have been made to fit on, and to effectively protect, a human head. (Protective headgear has also been made for horses, dogs, and elephants).

This is a human head. And this is what’s under the skin, a human skull.

(Image Source: Maksim Goncharenok on Pexels)

(Image Source: Bruno Galvão on Pexels)

This is a spotted hyena’s head. And a skull.

(Image Source: titiamatti on Pixabay)

(Image Source: The Skull Index)

A gnoll’s head should have some differences from a spotted hyena, mainly a larger brain case and the base of the skull being different because the spine is vertical instead of horizontal, but even so, it’s a very different shape from a human's.

The biggest difference is, humans have flat faces. Proportions vary a little from person to person, but we don’t really have snouts: our jaws are only slightly farther forward than our eyes, and our noses only slightly beyond that. Above your eyes, your forehead starts off very steep, almost vertical, and only curves back gradually. Our ears are also relatively small, and low on our heads, actually slightly below eye level. There’s a big, round dome of skull above our eyes and ears that’s a very convenient shape for a helmet to snugly fit over.

Hyenas, and by extension gnolls, do have snouts, and so should most humanoids with animal shaped heads. There’s a lot of face extending several inches in front of the eyes. A gnoll’s forehead also slopes backward at a shallower angle than a human’s, and their ears are not only larger than a human’s, but much higher on their heads. All these anatomical differences mean many of the designs we humans have come up with to protect our heads in warfare would just not work as well for a gnoll.

Let’s go over some designs of real life helmet, and how well they could be adapted to fit a gnoll. For these comparisons I’ll be using an approximate human head shape I got from a public domain silhouette of a head in profile that I added a hairline and eyes and ears to. The gnoll head shape I drew based on referencing photos of hyenas. These are rough approximations and the helmets won’t be perfectly accurate, but it at least gives a basic idea. The dashed lines on the gnoll picture show the ears in a folded back position. (Figure 1)

I’ll start with a simple skull cap (Figure 2). This is pretty much the bare minimum: a domed metal hat that covers your brain bucket and not really anything else. On a human, it’s… adequate, if not great. There’s a reason people with the resources and technology for more protective designs tended to not just stick with these. Everything below the eyes is totally exposed. On a human this includes the ears, so it’s relatively comfortable to wear and doesn’t restrict sight, hearing, or breathing, although they could be worn with other head protection like an aventail or coif. On a gnoll, this looks like a precarious fit. There isn’t a full hemisphere of skull above the eyes, so this might not stay on very well without a chinstrap. It also covers the ears. I’ve gone with a pointed design since it has more room for a gnoll’s ears to fold up inside it. This has some room for support webbing and padding so the steel isn’t resting directly against the head. It’s also not as protective for a gnoll. A downward blow glancing off the top of the helmet can keep going down and hit right on the unprotected upper jaw and snout, which is much less of a problem for a human.

One common way of improving the basic skullcap was adding a nasal bar: just a bar of steel in front of the nose (Figure 3). This is still not great at stopping thrusts or arrows unless you’re really lucky and it hits dead center, but it can at least catch a weapon somebody’s swinging at your face. Except for a gnoll, this bar has to be much longer and bulkier to offer “equivalent” protection, and I’m not sure it would really be equivalent. There’s nothing really securing the helmet against pivoting forward if a downward blow hits that long lever, forcibly driving it into the wearer’s face. It’d be better than having no protection at all, but still a lot of hits that would result in minor or no injury for a human could be pretty nasty for a gnoll. Having a wide metal bar in the center of the field of vision much farther ahead of the eyes would also be a bigger nuisance.

To add more protection to the nasal helmet, you can add more metal bars to the face approximately where the cheekbones are, connecting to the nasal bar and to the main helmet around the temple, creating a “spectacle helmet" (Figure 4). I’ve seen replicas of these advertised as “Viking” or “Norman” helmets a lot, although I have no idea how historical that is. These still have large eye holes and leave your mouth uncovered, which is good for vision and breathing but not great for protection. But the cheekbone bars could also have an aventail attached to them to protect your whole face, while still letting you breathe relatively freely if the cloth padding is omitted, or alternately can be further expanded into a full face plate (See Figure 5C below). These would work, ish, but again with a long muzzle you’d need more material and there would be more areas it didn’t protect.

Another common addition to simple helmets is some form of ear flaps or cheek guards, which can be hinged (as on many roman helmets) or fixed in place, or just lowering the sides and rear of the helmet to cover the ears. Modern examples include batting helmets in baseball, which cover the ears, and now often one jaw, or sparring headgear for unarmed martial arts like boxing. This should work pretty well on a gnoll, so well I’d even call it almost essential. Protecting the sides of the head is useful, although just like a nasal bar a cheekguard would have to be really big to not leave the front of the jaws vulnerable, but it just makes the helmet fit over the head better, and for a gnoll there’s not really a compromise of whether or not to cover your ears, because their ears are so high up that even a basic skullcap already covers them. Extending the helmet down the back of the head, as with sallets, roman helmets, Kabutos, lobster tailed helmets, etc, is also nice.

The final common modification to a skullcap to improve its protection is adding a brim. This could go all around the helmet, as on a kettle hat (Figure 6) or only on the front, like the brim on a burgonet or kabuto (Figure 5). This is a pretty good feature for an open face helmet on a human. It keeps the sun and rain out of your eyes, and it would catch most downward angled blows and block them from hitting your face, as well as blocking projectiles coming down from a steep angle, especially if you tip your head forward (Figure 5A). On a gnoll… it doesn’t (Figure 5B). It’s better than nothing, but the brim has to be absurdly long, longer than a modern baseball cap, to actually extend beyond the tip of the wearer’s nose (Figure 5D). This is a huge lever for an opponent’s weapon to catch, and could even deflect an upward angled blow that would otherwise miss into the wearer’s face. A side brim functions more like it does on a human, but I think it’s not as good as cheek plates because as mentioned above a gnoll’s ears are so high up they have to go inside the helmet either way so choosing a brim over cheekplates doesn’t help with comfort or hearing, and extending the sides of the helmet lower on the head helps it stay on.

So, now we’re through the relatively simple open-faced helmets. Let’s get into designs that offer more face protection. These have existed in some form for a while, e.g. the Corinthian Helmets, but I’m going to focus on late medieval Europe’s development of “knightly” helmets. If you start with a “spectacle” helmet, and then extend the spectacles into a full face mask, and then extend that further to wrap around the sides more, you’ve got an enclosed helmet. Make it cover the sides and back of the head completely, and you have a Great Helm (Figure 7). I’m sure you’ve seen these in memes about crusaders, or on Solaire from Dark Souls, or the Black Knight from Monty Python and the Holy Grail. These cover the entire face, which means restricted hearing, restricted sight, and restricted breathing, and if you want to breathe better, or see better, or drink some water, you have to take the whole helmet off. I haven’t put a lot of effort into a mockup of a gnoll version of this, because it just… doesn’t work very well. The whole tin can shape doesn’t fit on a creature with a skull that’s long instead of tall. You can sort of stretch it out to cover the muzzle, but this would make it heavier, more complicated to manufacture, and the whole thing has to be open at the bottom or you can’t actually put it on. The same is true of a human greathelm but a greathelm on a human doesn’t have much of a gap between the helmet and a coif underneath it. It’s difficult to effectively protect the underside of a gnoll’s head with pretty much any design, but a one piece closed face helmet is heavy, bulky, and not that protective.

Moving on, more advanced helmets very often featured some kind of movable visor, that covers the face when lowered, but can be raised to let you see better, breathe more easily, speak more clearly, drink some water, and so on.

One of the earlier examples of this type is the bascinet (Figure 8). In its basic form this helmet is open face, but covers the sides and back of the head, and is slightly pointed at the top. In practice these tended to be worn with a maille aventail which covers the neck, sides of the face, and chin. The rest of the face can be protected with one big visor, either attached with a single hinge at the forehead or two hinges on the sides, that swings down and covers the entire face. I’ve seen many different kinds of visors for these, and I don’t know how many of them were actually used historically, but they can physically be built as flat faceplates, rounded shapes, or, maybe most recognizably, a big conical visor called the “hounskull” or “pig faced” visor. With a name like “Hounskull” you might think this would be perfect for a creature with a roughly canine like face shape, right? Well… not really, no. The hounskull works fine on a human because the cone is full of nothing. The wearer’s face is flat, the shape is just there to help deflect attacks. If the space is occupied by the wearer’s muzzle, then a visor with hinges on the sides of the head can’t be lifted and lowered because the wearer’s chin gets in the way, so much like the greathelm it needs to be open at the bottom. Again, the chin is unprotected. Bascinets were usually worn with a maille aventail covering the neck and extending up to the chin, but it’s not really practical to do that with long jaws.

There are a few potential ways around this, but they have drawbacks. Extending the aventaille forward to cover the jaws with what’s effectively a loose fitting maille muzzle, or adding a partially detachable maille chin guard or hinged plate on the bottom of the visor could work, but either of those make it awkward and cumbersome. A visor hinged on the forehead, i.e. a klappvisor, can clear the wearer’s muzzle, but a full face visor for a gnoll would be very heavy and bulky and have a long lever to twist the visor and destroy the hinge if it gets hit. Obviously it’s better for armor to get damaged than you to get damaged, but a visor that falls off from a solid hit or gets twisted so badly that gaps are opened or the sights aren’t lined up and it hinders the wearer, so you have to discard it, isn’t as good as a more durable one. The klappvisor’s size and weight would also make it a huge pain to actually fight with it raised. The shape of an open faced bascinet is pretty functional for a gnoll, though: the swept back cone shape gives plenty of room for the ears, and it covers the sides of the head pretty effectively.

Another popular type of visored (sometimes) helmet is the Sallet (Figure 9). A sallet also protects the sides and back of the head, but doesn’t extend quite as low on the head as a bascinet, and even with the visor down the helmet might stop at roughly nose to mouth level. These tend to feature a continuous eye slit instead of multiple sights. Depending on the design the visor might extend up to the forehead and have a full eyeslit in it, or it might only have a plate below the eyes covering the nose, with the eyeslit being formed by a gap between the visor and the main helmet when the visor is fully lowered. Alternately they could be visorless closed face helmets with the visor and eyeslit effectively built into the helmet as a single piece, but the helmet could be tipped back on the head for full visibility. These all leave the chin exposed, but could be worn with a bevor, a piece of plate armor that protects the neck, chin, and lower face, and the bevor might or might not have an articulated piece letting you lower it to expose your mouth. This is overall a more flexible and easily configurable but less protective type of helmet. Because the bevor isn’t integral to the helmet and instead attached to the torso armor, it doesn’t move when you move your head. It’s supposed to overlap some with the visor, but some head postures can open up gaps that opponents’ weapons can fit through, and I’ve heard arguments against its use in modern armored full contact sparring because of that.

For a gnoll, a fixed one piece sallet doesn’t really work because it has to have a longer front to fit the muzzle and therefore is a bigger visual obstruction when tipped back on the head. An open face sallet works fine on its own, as does one with a visor if you’re willing to accept only partial face coverage. The visor being comparatively small and light is nice. However, a bevor that’s fixed to the torso armor isn’t functional for a gnoll. It looks okay in the picture, but in 3D, the long narrow bevor makes it impossible to turn your head and heavily restricts raising and lowering it. There were real life helmets that had this kind of restriction, such as great bascinets or frogmouth helmets, but the point of a sallet is compromising protection for mobility. If you have to give up being able to move your head, there’s no reason to wear a sallet which is less protective over a great bascinet that fixes the entire helmet to your torso and doesn't have potential gaps.

Another variant on the bevor concept is the Burgonet (Figure 10). As an open face helmet this features a top crest for reinforcement, pretty good cheek/jaw coverage, and a brim. I think this is usually fixed in place but I’ve also seen pictures of some where that’s on a hinge. Either way, the brim gets in the way of a conventional visor. Instead, the burgonet takes the bevor and extends the idea, literally. The bevor’s attached to the helmet, but with multiple articulated plates extending up to eye leve that turn it into a Falling Buffe: essentially a visor that opens downward instead of upward. This might work, ish, but it runs into the same damn problem as pretty much every one of these visor designs on a gnoll: the Falling Buffe would have to be enormous to clear the wearer’s muzzle.

Let’s move on to two types of articulated helmet that fit closely to the head and fully enclose it. The Armet (Figure 11) has hinged cheek/jaw guards that join together in front of the chin, covering roughly a similar area to the aventail of a bascinet. A movable visor, hinged on the sides, covers the rest of the face. This could, in theory, work for a gnoll, although the design limits opening your mouth a bit and it doesn’t work to wear it in fully open faced mode. The Close Helmet (Figure 12) has a similar idea but a slightly different principle: the front of the helmet covering the chin and neck, the bevor, is hinged on the same pivot point as the visor. I only have a picture of this one on a human, because it doesn’t work at all for a gnoll: it suffers from the same problems as a bascinet visor: the wearer’s chin gets in the way of lifting the bevor to take the helmet off.

Okay, back to the drawing board. Face protection designed for humans just doesn’t work with a long muzzle. You can’t enclose the entire head in a single rigid piece of metal without having a huge opening under the chin, all the partial face protection options for open faced helmets can’t cover the whole muzzle, it gets in the way of visors and bevors... how do we design something that does work?

Let’s go back to the basic principles of what makes a helmet design effective. The more of the head and neck are covered by sheet metal, the more protected you are, but you can’t just put a metal bucket over your entire head and call it a day. A helmet needs to have openings so you can see, so you can breathe, and ideally so you can eat and drink while wearing it. If you’re marching around for hours in heavy armor during a battle, hydration becomes a problem, and having to take your helmet off completely to drink some water isn’t great if there are arrows flying around. Also these are being designed for a fantasy setting where things like healing potions exist, so being able to remove the lower face protection quickly is actually a big deal.

If a helmet has face protection that seriously interferes with those things, then it’s better to have that face protection as a movable visor so you can open it if you need to without taking your whole helmet off. However, the corollary of that is that if something doesn’t interfere with breathing, vision, hydration, or taking the helmet on and off, then it can be fixed in place and doesn’t need to be part of a visor. For example, the bevor on an armet or close helmet, or the aventail on a bascinet, can come up past your chin and still be fine because you can still breathe and speak with the visor open.

I’m going to start with a basic open-faced helmet design. This is a bit like an open faced bascinet or sallet. It protects the sides and back of the head, as well as the back of the neck, and has a pointed top to make space for the wearer’s ears. This has no face protection whatsoever, but it also has basically zero restrictions on vision. The wearer’s upward field of view is slightly limited, but no more than basically any hat. (Figure 13A)

Now let’s add some basic face protection (Figure 13B). A nasal bar, cheek/jaw guards, or a brim could all have some value, but I think cheek plates make more sense than a nasal bar as the first thing to add, because cheek plates are a relatively small obstruction to peripheral vision, but a nasal bar is right in the center of the field of vision, and a gnoll’s binocular vision range is a bit narrower than a human’s as it is, so I think the nasal bar would be a more annoying visual obstruction. Also, because of what I mentioned above about these parts being a long lever that will turn the helmet on the head and smack them into the wearer’s face when hit, it’s better for any face protection of this type to be relatively wide and spread out the force of an impact more. Either of these can be bypassed, obviously, but if you’re forced to pick one, I think the cheek guards are a better option. For an open faced helmet with no visor, a front brim can also be added, which can block many of the same blows that a nasal bar would.

This still has room for improvement, though. If the cheek guards are extended out even further, they can be joined in front of the nose, supporting each other and giving protection against things like direct frontal impacts (Figure 14A). A nasal bar could also be added to this, creating the equivalent of a spectacle helmet, and once again it can be used with a brim. This does create a little bit of visual obstruction, but the part that’s in the center of the field of vision is mostly already blocked by the wearer’s own face. It still doesn’t restrict breathing either. Yes, it’s in the path of air, but it’s not trapping exhaled air close to the face, just deflecting it downward, and for breathing through the mouth it doesn’t even do that. It also shouldn’t get in the way of drinking from a canteen or waterskin.

With the joined jaw guards plus a nasal bar or brim, this should be pretty effective at stopping cuts and swings, but it’s still not great against thrusts or projectiles to the face. The cheek guard should probably be curled up at the top to make sure it catches a thrust glancing off it instead of deflecting it into the eyes, but there’s still a lot of area where an attack can get through. To address this, the massive vision hole can be turned into a narrow slot, or eye slit, which turns it into something resembling a fixed visor sallet (Figure 14B). The main drawback of this is that if you make the eye slit small enough to block a bodkin point arrow, it seriously restricts vision and requires the whole helmet to be taken off to see. I think a more practical solution is adding a movable visor (Figure 14C & 14D). A really nice feature of this design is that the visor can be much smaller and lighter than a bascinet-style visor or even a sallet style one, because it doesn’t need to cover the whole muzzle: the part over the nose is fixed in place, and the visor can come down and rest on top of that.

Just that addition makes the helmet protect really well against projectiles coming downward or horizontally: just tilting the head forward a little bit shields the wearer’s chin behind the jaw guard. However, there is still one weak point: upward thrusts or projectiles under the chin. Getting directly shot under the chin isn’t really a common angle, but arrows deflected upward by torso armor, whether intact or as splinters, are more of a danger. This, unfortunately, is a harder problem to solve. Every way of protecting that area I can think of requires some kind of side hinged or otherwise removable pieces. This could include a mask, a two part side hinged visor, a bascinet style visor that opens at the bottom, or various other options.

I think an armet style bevor made of hinged cheek plates is the most efficient way of doing it. Revisiting my “armet but for gnolls” mockup, the cheekplates actually cover the entire muzzle, allowing a smaller visor to be used. However, this design has a serious drawback: ventilation. Any fully enclosed visor will limit a fighter’s endurance by making you get out of breath faster, but I think this is a bigger problem for a gnoll than for a human because gnolls have fur and don’t have sweat glands all over their bodies. When wearing armor over most of the body, including the ears that would otherwise be a heat exchange surface, being able to get rid of heat by panting would be pretty important, so a helmet that traps exhaled air would be a recipe for heatstroke. Opening the bevor would help, but a design like this would also be awkward to fight in with the bevor open.

I think this can still be improved though, by combining the armet and close helmet designs a little and using a two part visor on top of an armet style bevor (Figure 15A, 15B, 15C). Now the bevor covers the chin but still lets you breathe and speak (drinking’s a little tricky without a specially curved straw on a waterskin or something like that), the lower visor covers the mouth and nose, and the upper visor covers the eyes. It’s complex, but there are armets with two part visors IRL. Figure 15D is one last design, an open faced helmet which leaves the ears partially exposed. More on that below.

There is one thing I haven’t addressed in the reasons to have an open helmet: using your jaws as a weapon in combat. The reason I haven’t addressed it is… it’s not that good. Having a hyena like bite force, plus jaws that can physically fit around much larger things than a human’s, so you can stab someone with a sword and then rip their throat out with nothing but your bare teeth, sounds really badass and metal, but speaking of metal… armor. Armor exists. If you’re wearing a helmet with serious face protection and fighting in armor, there’s a good chance that your opponents are also wearing armor, and armor is very effective against teeth. Even textile armor: that’s what dog bite suits are. Maybe a hyena’s bite force would be enough to still break someone’s arm through gambeson or maille, but if an opponent has plate armor, even bone crushing teeth are still made of teeth, and therefore planning on using your jaws as a weapon is kind of like planning to use your fists, sans gauntlets, in an armored duel. Biting could occasionally be able to do something, but ultimately it’s a weapon with less reach and less lethality against armored opponents than a dagger.

One other thing I’ve omitted from this discussion is that head armor made for creatures with long skulls does actually exist in real life: armor for horses, i.e. barding, does include head protection. The horse equivalent to a helmet is a chanfron, and these do indeed typically cover most or all of a horse’s snout, but only cover the top of the head and are open at the bottom. These don’t fully enclose the ears like I’ve been assuming up until this point, and instead often have protrusions that guard the ears against frontal attacks but are otherwise open.

However, there are a few reasons I don’t think horse armor can be compared to armor designed for a humanoid with a non human shaped head on a 1:1 basis.

First: while warhorses were very expensive investments, they were not human beings, and were still more expendable than the knights riding them. To an army, of course, human beings are also expendable, but in medieval and renaissance warfare many/most fighters, especially ones who were wearing things like armets, bought their own equipment, and the protectiveness tradeoff is different.

Second, protruding ear guards have the potential to catch an opponent’s weapon, which can increase the risk of head or neck injury from energy transfer even if a hit is stopped. I think this is less of a concern for a half ton animal that has a proportionally large head and strong neck than it is for an approximately human sized humanoid.

Third, horses are quadrupeds, and in a typical head posture, the “top” of the head is in front of them. That’s where arrows, lances, etc. are likely to hit, which is also true of a long skulled humanoid if you lower your head a little, but it’s more extreme for a horse, and their different posture also means the chest or neck armor can’t really deflect something into their chins. Actually hitting the unarmored parts of a horse’s head would require you to be to the side and/or right next to the horse. To the side is probably a very difficult position to be in without immediately dying if the horse is in a formation of cavalry with other riders to either side, and being right next to the horse trying to stab it under the chin is also not a good position to be in because that means you’re in kicking and trampling range.

Fourth, warhorses aren’t really standalone combatants. If someone’s fighting an armored horse there’s also an armored guy on its back to worry about. While I’m sure people did try to target horses if they could get away with it, being right in a horse’s face trying to stab it under the chin is not only within reach of the horse’s hooves, but also within reach of the rider who probably has a sword or mace or warhammer, so ignoring the guy with a weapon to try to hit the horse’s weak points seems like something only somebody going “Screw it I’m dead anyway, hopefully if I take the horse down with me it’ll save my buddies from being killed by the knight.” On the other hand, if you’re fighting a person in armor, you absolutely will try to exploit any gaps in their head protection.

I do think the ear guards on some chanfrons do have some transferability to a combat helmet for a humanoid, as do some “open-ear” designs. It’s a sacrifice of protection for comfort and situational awareness. The major vulnerability of those designs, however, is not just injuries to the ears, but the gap in the helmet that’s protecting your skull. Ear guards in front of the ears would probably stop a strike with a broad blade like a sword or axe, as well as most thrusts to the face and arrows coming in from the front and at lower angles. The ear holes could be stabbed, especially in grappling, but for an open faced helmet your face can also be stabbed. I think the biggest danger is that a typical descending strike with a weapon that has a spike perpendicular to the haft, like a pollaxe, would be at the perfect angle to stab you in the skull. The effectiveness of ear guards also isn’t the same for every species. Horses have relatively small ears which are easier to protect, but hyena ears are both tall and wide. After fiddling with it for a while, I think the only open-ear design that really works is a full “crest.” 0laffson on DeviantArt has made some really cool designs for feline characters that use a crest for ear protection. I went with something kind of similar, but giving the crest a backward swept shape. Having the crest made in two parts that connect to a central ridge would help support it, and an open eared design is both inherently less protective and gets in the way of a visor, so I’ve chosen to to make the open eared helmet basically an open face burgonet. I think the ear crest would be made of metal, and have a rolled edge to help stop enemy weapons from biting into it it and transferring all their energy into the wearer’s spine, but it’d be relatively thin material that can bend and flex in an impact, because what it’s protecting is also soft and flexible.

In summary: the most protective helmet possible for a gnoll, other than something super specialized like a Great Bascinet that completely sacrifices head mobility, is probably an armet style design that uses side hinged cheekplates to protect the chin and throat. There are other possibilities like a burgonet with a bevor that's a fixed part of the helmet, a bascinet style visor or greathelm with a hinged door on the bottom, or some other side hinged visor or mask, but basically anything that protects the chin is going to require multiple moving parts and multiple steps to put on and take off.