Sacrifice enablers for EDH
There are tons of options: 

Attrition or Blood Rites, while requiring to pay mana, would kill your opponents creatures (or the opponent himself in the case of the rites). If you need something that doesn't require mana to activate you could try Bloodthrone Vampire, Carrion Feeder or Devouring Swarm.

Hell's Caretaker can be an interesting choice, because it gets creatures back when sacrificing others, but can be activated only once per turn. 

Lyzolda, the Blood Witch can be sweet, drawing you cards when sacrificing black creatures or dealing damage when sacrificing red ones.

There are lots more, here you have Magiccards search of creatures that have an activated ability which requires to sacrifice a creature and are black, blue or red.