User can create darker versions of things they touch

Pros:
-user can control what they create
-user can make darkness spread
-user can use powerful emotions as a tool
-user can control targets
-user can enhance targets
-user can travel through shadows

Cons:
-user will be consumed by power with overuse
-user can't control spread of darkness
-darkness will tempt user
-user will despise light
-user is likely to be power hungry

Weakness: light form
These two quirks balance each other and nullify the effect of the other

Nightmare Sans