I thought, what if there was a vengeful spirit% or, Mothwing Cloak% ? The run begins on when the first cut scene finishes, and ends when you obtain the stated item.

Hey, we already have a category that is essentially Mothwing Cloak% (Aluba%), where the goal is to kill the aluba behind the hornet arena. With the other idea, as for all category ideas, it won't be considered unless there's significant interest in it from runners of the game.