this video is specifically talking about the religions in MH G1 canon that one could prove to have physical character exist in the MH world, like could I meet Athena (yes).
this post is me expanding on what was discussed in this video. This post is not a replacement for the OG video, this is supplemental if anything. If I miss something, feel free to add to this discussion.
Before I say anything, yes, the characters in Greek Mythology are real characters you can meet in MH lore. Watch the video, I'm not talking about EVERY character with connections to the greek cause there are almost 20.
HOWEVER, I will be addressing River Styx as she is only greek in name and aesthetics alone (as far as I'm aware) River Styx is the daughter of the grim reaper. The grim reaper is the personification of death, not tied to any one religion. The grim reaper is not a god. Death is personified in the Bible book of Revelation, but at no point is the grim reaper and death the same person or connected in the bible. Although death is in the bible as a concrete person, the grim reaper is not death nor is the grim reaper in the bible. and since we never meet Death in MH G1 and since Death is not a character or a physical being, christianity has still yet to be proven in MH canon.
HOWEVER, I could be wrong, but I do not recall any evidence that anyone in the MHCU WORSHIPS the greek gods and practices greek mythology paganism. (Please correct me if I am wrong, I genuinely cannot remember any examples)
So Greek Gods are real characters, there are Greek magic and powers, but the practice of greek pagan religions in MH G1 is unproven ATM.
The religion and practice of ancient Egyptian gods is a canon Cleo says "Oh my Ra" meaning it is a canon belief system, the fact that she was mummified also proves the practice but mummies as monsters and undead (i do not believe) are a belief in said practice (i don't think living undead mummies are in Egyptian mythos, i think that is a western culture invention to demonize and make the pagan exotic religion look savage and barbaric) , so i don't think we could use Cleo as proof that Ra is real in MH.
Even IF mummies aren't a part of the beliefs, the magic and powers ARE real because Cleo uses curses throughout ALL gens. The powers and religion are real even if we can't concretely prove their gods are.
zombies and ghosts are prevalent in so many religions, and the version of these species we get in MH are so generalized that they are rarely if at all tied to a specific religion. The only example of a zombie tied to a religion is Cleo. The others are so generalized, they aren't exclusive to one religious belief and cannot be used to prove one religion over another.
Furthermore, the MH Haunted movie disproves most afterlives if anything, so the existence of an afterlife cannot be used to prove the existence of any physically concretely real gods.
The same can be said about vampires and werewolves as they are a generalized folk belief and superstition of historical peasants. This does not prove the existence of specific afterlives. FURTHERMORE, the existence of physical vampires and werewolves do not prove that humans told these folk tales or had these spiritualities. We know that monsters and norms have tensions (see Draculuara's backstory and Ghouls Rule) but no evidence of folk tales being told.
HOWEVER, The Dracula book canonically exists in MH. In Draculaura's diary, she tells us that Bram Stoker stole her father's name for the character in the book, but the book is not a historical account, it just exists as a folk tale.
YET, the book still exists in MH, we can assume Bram Stoker wrote the same novel about Christianity being used to fight back against vampires, so does that mean the belief/practice of Christianity is a canon in the MHCU?
Also of note is Rochelle Goyle as Gargoyles are a similar french countryside peasant folk farmer superstition, similar to The Legendary Loup-Garou (one origin of folk werewolves).
Unicorns like Nathan Trotter also fall under the same peasant belief of vampires, werewolves, and most cryptids.
Hoo Dude is a living Voodoo doll, BUT in webisode canon, Frankie brought him to life with science, BUT the voodoo doll properties are real and are used, proving some sort of magic/power. HooDoo is a folk spirituality like wicca, not a religion. Voodoo is a closed practice religion which (as far as we know of Gen 1) white girl European Frankie (Geneva, Switzerland where Victor grew up and Ingolstadt, Germany where Victor creates his monster) has no right to practice the African creole religion or spirituality meaning Frankie canonically commits either heresy or cultural appropriation in MH G1 canon. (But being only 16 days old, she's naive and probably doesn't know what either of those terms mean)
Even if, the power behind HooDoo and VooDoo are provably real, there is nothing that implies that the african/haitian gods are. Yet, one could argue that the magic wouldn't exist without the gods being physically real. At best, the power is real and the physical god being real is a theory with proper scientific argumentation backing it.
The same can be said about Skelita Calaveras who has a Skullector or "Howliday" Edition Doll which celebrates the Mesoamerican-rooted Día de Muertos which is from the combined spirituality of Roman Catholicism with ancient Indigenous Mesoamerican beliefs (primarily Skelita has a confirmed Mayan ancestor). This proves the spiritality and that a mexican Land Of The Dead is real, but this does not prove the existence of any physical dieties of either Roman Catholicism or Mesoamerica.
Isi Dawndancer is of Indigenous North American Tribal Religions, and in her diaries, she interacts with Coyote the trickster spirit (source her diary). So the gods and spirits of Indigenous North American Tribal Religions are real physical beings. (Also their folk magic is physically real too)
Similarly, Jennifier Long- Chinese dragons fall under this Mesoamerican belief theory as a modern cultural spirituality more than a religion in which the dragons are nature spirits like Indigenous North American Tribal Religions. An arguement could be made for ancient chinese mythology but the dragons are more a generalized species like the djinn more than one mythological figure. A MH equivalent example would be Ava Trotter, Iris Cyclops, Gorgon species, nymphs… We have proved that the religion and spiritual exist, but the proof is once again theoretical if the characters of these beliefs are physically in the world of MH like VooDoo/HooDoo and Mesoamerican theologies.
GiGi- A djinn (also jinn or anglicized as genie) is a supernatural spirit in ancient Arabian and Islamic mythology (so like an angel to Christians) does that mean the arab and islamic gods are real? Djinn are in the Quran. So Islam faith is canon. If a creature from the Quaran is real, does that make the rest of the Quaran non-fiction? Does that prove Allah is a physical being you could meet in MH G1? Islamic faith is an Abrahamic religion, from the Prophet Abraham. If Abraham is a canon character of monster high, does that mean all the Abrahamic characters are canon? Judaism, Islam, and all branches of Christianity? But GiGi is also a genie which is the westernized version, which could negate all of that and exist seperate of any association with Arabian and Islamic faiths.
Hex Steam is related to fae ancestory of the court of Fae under Oberon and Titania (characters from Shakespeare's A Mid Summer's Night's Dream) and are of Celtic Paganism (Ireland and Scotland which is references in many of shakespeare's other works) in which all fae of this mythology pagan religion are decsendants of The Goddess Danu which is of Celtic Paganism and Wicca.
Like all the greek gods and MH, if Oberon and Titania are now MH characters, Danu HAS to be a MH being, meaning Celtic mythology, Celtic folk tales, wicca is canon as a spiritual practice and a physical provable religion.
Even IF you don't agree with Hexicia Steam being fae, Scara Screams is a banshee and a direct descendant of Danu.