Just finished the game with a friend and I believe I saw everything, maybe I need to play once more ignoring a certain someone.
SPOILERS AHEAD!
but first: This. Game. Is. Amazing. Temmie, your art and story are beautiful.
BEAST-Type's Origin:
So, in the last half of the game, it is clear that BEAST-types are not from this world. And Zera is the one behind it (probably). Yoki is most likelly a BEAST-Type, and a strong one.
The world is clearly not made for Yoki, She cannot access the battle system and some assets on the game, like the enemies and the healing water pools, are not meant to be used by her, but rather seems directed to the 4 heroes party Yoki meets. This game world is made for these characters, and the some other characters, Like Yoki, are from another game (or world, as stated on the game). The heroes also have unique portraits, like protagonists on a RPG game. Yoki and some other characters also have portraits but are different.
So if some characters are not from this world, like Zera pulling the Lonely Girl from another world to this (I'm yet to play Escaped Chasm xD), BEAST-Types are anomalies, and Zera is most likely bringing them in and using them. But is Yoki and the others enemies the heroes faces BEATS-types? or are they something else, a fourth type? But they are surely the same thing.
Also, Witchcraft seems to be Meta-game knowledge, like knowing how to open a battle menu and etc... Maybe is the other way around and the dark lord is actually from another world (bringing Witchcraft as they powers are anomalies).
The Dark Lord:
My theory is: The Dark lord is Charles, and the ones following him are the heroes. He flees for the West and make the dungeons or enemies or something... but I could not gather a lot of information here.
The Lonelly Girl:
When meeting Temmie after the credits, she allows us to play as the wolf girl. I have not played Escaped Chasm yet but a friend told me the jist of it. She is after Yoki for some reason, maybe she remembers something about the many eyed demon we meet at the end game, that is most likely yoki's sister, and because of the scent the Wolf Girl recognizes Yoki and her mind now as a beast is making she have this relationship with her... who knows.
Extra crystal:
There is an extra crystal at Zera's home, what was his relation with the Dark Lord? wasn't he the Dark Lord all along and he just lied to us at the end of the dungeon? ...
Final Crazy theory:
Final point, it is possible that this game, when calling other games as other worlds and having all this meta-game gameplay and story, specially when dealing with Temmie and Toby Fox. Is this game a shared universe where different worlds coexists, and them it can share the same ecosystem as Undertale and Deltarune worlds??? I'm sure there are multiple worlds on Temmie's story, but would she make it so that her story and Toby's stories could be canon??? (maybe it is a little far fetched, but theories of other universes existing and out of places characters like Gaster, and BEAT-Types being called another name on other worlds (monsters vs humans??) and etc... the more I think about it, the most sense it makes.) . But of course this can be a single universe Temmie is creating for all her "worlds", and I cannot wait to see this being developed into a complex storyline!!! XD
Thats are some of my thoughts right after playing the entire game. Now im trying to beat it while ignoring Zera but I dont know if it is possible to do so...
Anyways, thanks for reading!!