Kyros, The Infinite Cycle

Flying, Lifelink, Ward {2}

Whenever you cast an instant, enchantment or sorcery spell, destroy all other creatures you control.
Each permanent destroyed this way reduces the mana cost of your next instant, enchantment or sorcery by {r}, {b}, or {u} based on it's color.

{p/r}{p/b}{p/u}: Pay X life, where X is the CMC of target creature you control. Target creature gains indestructible until end of turn.