Karotu, Glistening Oil Eater

Companion, Hexproof
At the beginning of your upkeep, you may move up
to one counter between any two targets of the same
type on the battlefield. If a counter is moved to or
from an opponent or a permanent an opponent
controls this way, you lose 2 life.

{x}, {t}: Karotu, Glistening Oil Eater deals {x}
damage to target creature or planeswalker, where
{x} is the number of poison counters you have.