Yep...now everyone's talking about the Nightmare Rarity that happened in the comics...I think I like yours more though. I'm getting a fic idea that involves Ponyville becoming infected by the darkness, turning many residents, including the mane 6 (except Twi) into Nightmare forms, and she has to fight the darkness, with only her element of Magic. Will she save her friends? Time will tell...
i have a better name for her and a back story! instead of infestatia, you should call her Onyx Heart! an onyx is a black gemstone so black heart, witch is the opposite of generosity, but has a gemstone like rairity! and she was out gem hunting when she found a huge black/purple amethyst, when she touched it black energy shot down her hoof and turned her into Onyx Heart!
p.s. i hope you don't mind the fact i used nightmare twi as my profile pic, i will change it once i find a good pic of nyx
Isn't Spike actually supposed to be relevant to the plot of that arc, rather than serving as a sarcastic narrator? I heard he was supposed enter full on Super Mario mode in order to save her from that.