To put it rather simply, it is Twilight (or Rapidash) Sparkle and Blaze the Cat together in one crossover.
This was suggested by, and as such is a gift for,
Twilight and Blaze's underground search for some particular gems took a turn for the unpleasant with the arrival of some familiar foes. Irrritated mildly, the two partners released thier, um...hotter side as they threatened to deal with thier enemy in a rather painful way.
My Little Pony: Friendship is Magic is owned by Hasbro
Blaze the Cat is owned by Sega