Rakdos, Patron of Chaos

Flying, trample
At the beginning of your end step, target opponent may sacrifice two nonland, nontoken permanents. If they don't, you draw two cards.

Legate Lanius, Caesar's Ace

Decimate — When Legate Lanius enters the battlefield, each opponent sacrifices a tenth of the creatures they control, rounded up.
Whenever an opponent sacrifices a creature, put a +1/+1 counter on Legate Lanius.

Black Market

Whenever a creature dies, put a charge counter on Black Market.
At the beginning of your precombat main phase, add {B} for each charge counter on Black Market.