Hot Potato

Cumulative upkeep {1} (At the beginning of your
upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
At the beginning of your end step, an opponent
of your choice gains control of hot potato.
Whenever hot potato would leave the battlefield,
it deals 10 damage to you and each creature and planeswalker you control.