OK feathersnakes, wrap your coils around something solid and stationary because this ride is about to get wild! Before things get more complicated understand that all life in this place is made up of three things:

Soul which holds personality, memories, in all sense the 'you' not defined by physicality.

Physicality which is exactly what it sounds like, bound and defined by the next thing, essence

Essence is life force, essentially. Everything has it- plants, animals, certain phenomena in the natural world. It's also what the mages use to work magik.

In short: Soul and Physicality are two pieces of fabric, Essence is what stitches them together.

On Haidren's continent and in most of his world, the apex predators are wyrms: huge creatures a bit reptilian and a bit insect, and a whole lot of teeth. All of them are various levels of venemous. On his continent at least there are five in order from smallest to biggest: River, Common, Blind, Great/Greater/Crowned, Sea. Seawyrms have less venom because of their sheer size.

Onto the Blindwyrm! Blindwyrms are pretty fucking huge. I haven't worked out feet/meters but in general large enough to take down a horse with no problem. This is a pretty accurate size portrayal of an adult, but certainly not the upper size limit [they tend to keep growing].

They aren't actually truly blind, their headshields conceal rudimentary optics that are mostly light sensitive. Basically they can tell daytime from nighttime and everything is a large blurred mass. Why can they get away with being 'blind'? Because they are geared to hunt essence. They eat it- they basically drain the lifeforce from things, and that fuels them with enough 'life' to make them veritably immortal. This also makes them the best natural mages out there.

Did I mention they're smart? Like, higher order intelligence. They don't have a spoken language, but they 'talk' to eachother silently via essence, usually sending complex images and feelings. They are smart enough to use 'facades' to hunt: they use essence to manipulate their physicality and mask themselves as a tree, a deer, rocks, and even humans [which is how Haidren happened, but that's another kettle of fish].

They are pretty heavily armored because Greatwyrms prey on them a lot [being of relatively similar size] and it's not unknown for there to be spats between Blindwyrms. They also naturally repel magik, curses and glyphs literally slide off them. It makes sense for something that preys on the strongest magikal things around them to be resistant.