Niv-Mizzet, Guildpact (Murders at Karlov Manor)

Legendary Creature — Dragon Avatar - Flying, hexproof from multicolored
Whenever Niv-Mizzet 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.