Nimb, Cloud Elder

Flying, Lifelink
When Nimb enters the battlefield, create X
Blue White 0/1 Dragon Spirit Creature tokens
with flying and "When this card dies, draw a
card", where X is your floating mana.
Nimb's Power and Toughness are each equal
to the amount of floating mana you have. You
don't lose unspent mana at the end of
your turn.