Demon of Dark Schemes
{3}{B}{B}{B}
Creature -- Demon
5/5
Flying
When ~this~ enters, all other creatures get -2/-2 until end of turn.
Whenever another creature dies, you get {e} (an energy counter).
{2}{B}, Pay {e}{e}{e}{e}: Put target creature card from a graveyard onto the battlefield under your control tapped.
Festercreep
{1}{B}
Creature -- Elemental
0/0
~this~ enters with a +1/+1 counter on it.
{1}{B}, Remove a +1/+1 counter from ~this~: All other creatures get -1/-1 until end of turn.