Navandrin, Conclave Colossus

Indestructible, Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Whenever you gain life, you may pay {x}, where
X is less than or equal to the amount of life you gained. If you do, create X 3/3 green Centaur creature token.