The design itself is awesome but I have a concern: many minute details will probably be lost in the sprite (like the pupil, the pattern around the eye or the smaller details of the “horn”). And what colors should they be?
As for balance: they seems pretty fine for me, Evil Spell is interesting. It’s good against special attacker but less accurate than Will-o-wisp. The ability Hate is strong on the offensive if you have a movepool with good coverage, but kinda useless on the defence (let’s be honest, if Gardevoir receive a supereff attack, it won’t stay on the field for long, and Fairys have a lot of good special attacks + a very strong physical one, as much as I love the mon, it’s not very tanky) - the thing is, the typing is a good defensive combination, so I guess it balances out?
Overall, a good design on paper, it’s clearly the pokémon you intended but with enough flavour to make it different, the only issue I see is again how the minor details that makes it stand out will probably be lost on the sprite sadly.