First off, I love that you are doing this, and I like a lot of the suggested ideas so far!
I have some ideas, hopefully they don't sound too bad or too broken, haha!
Sableye Crest: Makes user take double damage from Fairy type moves, base speed stat increased to 140, base attack stat increased to 110, base special attack increased to 110.
Basically doubling down on Sableye's weakness, but rewarding it by becoming one of the fastest attackers in the game. Traditionally, Sableye is known as a supportive, tanky Pokemon, both in Mega and normal formes, so having a form