Zentaros, the Convergence of R

Whenever you cast a spell, you may choose one of the following: Change the spell's color identity to any color(s), or, change the spell's mana cost to {X}, where X is the number of colors in your mana pool. Legendary creatures you control get +1/+1 and have "Tap: Add

Converge—{t}, Sacrifice a land: Search your library for a land card that shares a color with any color of mana in your mana pool and put it onto the battlefield tapped. Activate only once each turn.