Niv-Mizzet, Guildpact {W}{U}{B}{R}{G}
Legendary Creature — Dragon Avatar
Flying, hexproof from multicolored
Whenever Niv-Mizzet, Guildpact deals combat damage to a player, it deals X damage to any target, target player draws X cards, and you gain X life, where X is the number of different color pairs among permanents you control that are exactly two colors.
6/6