Death Grasp

Whenever a creature attacks one of your opponents or a planeswalker an opponent controls, that creature gets +2/+0 until end of turn.

Whenever this creature blocks, exchange its power and the power of target creature it's blocking until end of combat.

At the beginning of each end step, each player gains control of all nontoken permanents they own.

Players can't gain life. At the beginning of your upkeep, this enchantment deals 4 damage to you. At the beginning of your end step, target opponent chosen at random gains control of this enchantment.