Anti-Venom, Deranged Healer

Menace
Remove a +1/+1 counter from this: Prevent all
damage done to any target until end of turn.
Symbiote(When this enters the battlefield, sacrifice
this unless you put it over a creature you control. Put
a +1/+1 counter on this for each of their shared colors.
When this leaves the battlefield, return that creature
onto the battlefield with a -1/-1 counter for each of
their non-shared colors.)