The Consuming Shadow (An Idea, please give feedback)

Hi! It's me! It's been fucking ages since I've done anything meaningful here, but now I'm here to discuss with you an idea based on Yahtzee Crowshaw's (yes, that one) "The Consuming Shadow," a procedurally-generated survival horror game with a lovecraftian theme. As the game's protagonist can put it:

"A shadow is trying to enter our world. One of the Ancients. The runes confirm it. I don't know which one. All I know is that they arrive at Stonehenge, three days from now.

I know what I must do: explore places touched by the Ancients, assembling clues to piece together the banishment ritual and the identity of the invading god. But I'm not sure how I know this. I have the strangest feeling that it might because I've already done it."

Playing it through several times has put me in the mood to write some very disturbing shit. I'm thinking about doing an MLP crossover with that concept, but I am wondering about who I would want as the protagonist... There would be no human characters, save for possibly human cultists that the Shadow has brought there.

My first choice is Twilight, but the thing is... I'm way behind on the show. I don't know much about her beyond what I knew for Saints and Sparkles. The last episode I saw was The Mane Attraction, and that was last November. Haven't seen an episode since, and don't really have the means to reliably watch episodes for free (if I ever bring myself to). I also have to wonder about her friends, since I don't really want to include them, but I imagine she wouldn't leave them behind on her quest to save the world.

So my other thought is Celestia, but she seems a little too knowledgeable...

What do you guys think? I'm looking for a pony who is capable, but also smart enough to actually put the pieces together of the puzzle and is of relatively sound mind. It's not fun to drive a pony insane if they're already halfway there.