Proto Long Legs

Defender
Every creature blocked by Proto Long Legs gains
1 Rot counter. (If a creature or artifact has three or
more Rot counters, they are destroyed at the end of the
next turn after they gained their third Rot counter.
None of this applies if the card is an Ooze. Instead,
during your upkeep phase, you may switch out two
Rot counters for a +1/+1 counter.)