I understand that this Tirek pretty much only shares the name with the show character, but it still sounds so awkward to any Lovecraft fan to have a characters based on a great old one and an outer God truly in service to that. Also awkward for an mlp fan to see Tirek like that. Neither original or g4 tirek fit that role well, it may have been better for sirwritesalot to just make up an OC instead of making his own version of Tirek. Then again Eric Cartman could command Cthulhu so what do I know? That minor complaint aside the stories themselves look pretty awesome and your art gives a really epic feel to it. I like the idea of the magic of friendship being pitted against a great old one, friendship and harmony are everywhere and transcend time, world's, and dimensions so I think they have a chance to undo the Unspeakable. The great old ones are still subject to cosmic and primal forces and harmony qualifies. Nyarlath, however, maybe they could banish an avatar? And if Tirek is set up as a supreme dark entity like Azathoth or Yog Sothoth then the best they can do is keep him inactive and defeat his minions. If you are researching Lovecraft I recommend the Cthulhu respect thread on vswiki, it gives an idea of the defined power and character of mythology creatures, which is hard to pin down since Lovecraft left them vague. I also recommend looking up darkest dungeon for a more defeatable but still eldritch vibe.