Kafka, Master of Souls

At the beginning of combat on your turn, gain control of up to one target creature until end of turn. Untap that creature. Until end of turn, it gains haste and "Whenever this creature deals combat damage to a player discover 4."

At the beginning of your end step, put a bounty counter on kafka. goad up to X target creatures your opponents control. where X is the number of Bounty counters on the battlefield.