Zanka No Tachi

Bankai (creatures with 2 or fewer colours in their
mana costs cannot have more than one Bankai
attached to them)

Whenever enchanted creature attacks, draft a card
from Zanka No Tachi's spellbook into your hand.
you may cast that card without paying its mana cost
until end of turn. If an enchantment was drafted
this way, you may only attach it to the creature this enchantment is attached to.