Ulrask, Spirit Extractor

Sacrfice a creature token , add {b} or {w}
to your mana pool, this mana can't be spent
except to cast spells.
Whenever you cast a spell, if no lands were
tapped to cast it, destroy up to 2 target creatures.
{w/b} : Create 2 1/1 black and white skeleton
tokens, sacrifice them at the beginning of the
next end step.