Yurei

Bestow {3}{w/u}{b/g} (If you cast this card for it's bestow cost, It's an aura spell with enchant creature.It becomes a creature again if it;s not attached to a creature.)
Flying
Yurei and enchanted creature gets +1/+1 for each Spirit or Arcane cards in your graveyard and has "Spirit or Arcane spells you cast cost {1} less to cast for each spirit or arcane spell you've cast this turn"