Mithril Sword

Attach this card to a creature you control.
If you attach this card to a creature with {w} needed to summon it, don't pay {w}{w}. If this monster has {b} needed to
summon it, add {1} to {x} for every {b} used to summon it.
Subtract {1} from {x} for each creature your opponent controls with at least {b}
needed to summon it. Pay {x}.