Contagion Engine
{6}
Artifact
When ~this~ enters, put a -1/-1 counter on each creature target player controls.
{4}, {T}: Proliferate twice. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)
Roalesk, Apex Hybrid
{2}{G}{G}{U}
Legendary Creature -- Human Mutant
4/5
Flying, trample
When ~this~ enters, put two +1/+1 counters on another target creature you control.
When ~this~ dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)