A servant form of Yggdrasil would need to be created first. It would make more sense for the Nighoggr to manifest if Yggdrasil got summoned.
I think rather than do that "personify a concept" thing they'd be better off with an event where we travel with Ratatoskr between Vedrfolnir and Hræsvelgr at the top, and Nidhoggr at the roots. Or maybe something way less literal. It could be a literal tree or some sort of manifestation of Yggdrasil exists exists that, as one of many in a cycle, chain summons three other beings with it. Hræsvelgr allegedly exists to protect Yg, Nidhoggr allegedly exists to destroy it, and Ratatoskr manifests as an intermediary. I say allegedly because some versions of norse myth portray it as Nidhoggr having a pretty cruel fate for its crime of trying to defy death by leaving Hel, being trapped within Yggdrasil's roots for all eternity and gnawing on them until it weakens the tree enough to herald Raganrok. Other versions portray it as a serpent that much like Satan in Dante's Inferno, chews on the corpses of the worst sinners, and for its suffering in that ordeal gets to rise from the corpses during Ragnarok as a Phoenix does ash, born anew. Meanwhile the eagle is portrayed as everything from Guardian of Heaven who enforces Nidhoggr's imprisonment and creates the winds of the universe, to an arrogant jerk who constantly picks fight with those around it and uses Ratatoskr to send tormenting messages to Nidhoggr.
What I'm saying is there's a ton of potential for nuance and subversion that I'm sure will never be used if any of them get in.
I actually a long time ago, like as in mid-late 2020, also came up with an idea for Beast V being Loki: Beast of Revelry/Chaos. The twist is that he's actually Beast V. Defeating Loki is like defeating Tiamat's Brain: you haven't stopped anything, you've just set off the REAL cataclysm. When Loki is defeated it sets off Ragnarok and summons his 3 infamous children: Beast V-1: Fenrir Beast V-2: Jormungandr Beast V-3: Hel - Fenrir, who devoured Odin and destroys the realm Asgard, seeks out and destroys any divinity that exists in the singularity. - Jormundandr, who poisons the oceans and destroys the continents as he rises from Midgard, wreaks havoc on the earth itself much like Tiamat's flood. - Hel, who gathers the dead and rules the underworld and had no stated role in Raganrok because she was a much later addition to norse myth sets to wipe out all life that escapes the other two by raising the dead to do her will and harvesting the souls of the living.
TLDR, the beast isn't truly Loki, it's all of Ragnarok and the true challenge is to deal with everything everywhere going wrong at once. Loki is just the one who harbors the twisted love for humanity that a Beast requires, that being the belief that complacency is evil, and that for Mankind to advance is not enough, they explicitly advance in the face of adversity for their advancement to mean anything, falsely believing that only when something is wrong will people look for new solutions to their problems and only through crises can mankind grow. In stopping a crisis that even the gods could not overcome, it would be the ultimate proof that Loki's "tests" are no longer needed.
