Corona, Rage Dragon

Flying
Sacrifice Corona, Rage Dragon when it enters
the battlefield unless you have 50 or more Rage
Mana.
10 Rage Mana : Put a -1/-1 counter on up to ten
target creatures. Gain one life for each counter distributed this way.
When Corona leaves the battlefield, gain 20 life.
If he is your commander, you cannot play Corona
for the rest of the game. Life gained this way
reverses commander damage.