Accursed Centaur

When Accursed Centaur enters the battlefield, sacrifice a creature.

Helm of Possession

You may choose not to untap Helm of Possession during your untap step.
{2}, {T}, Sacrifice a creature: Gain control of target creature for as long as you control Helm of Possession and Helm of Possession remains tapped.

Cabal Therapy

Choose a nonland card name. Target player reveals their hand and discards all cards with that name.
Flashback—Sacrifice a creature. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Treachery

Enchant creature
When Treachery enters the battlefield, untap up to five lands.
You control enchanted creature.

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Kjeldoran Dead

When Kjeldoran Dead enters the battlefield, sacrifice a creature.
{B}: Regenerate Kjeldoran Dead.

Reins of Power

Untap all creatures you control and all creatures target opponent controls. You and that opponent each gain control of all creatures the other controls until end of turn. Those creatures gain haste until end of turn.

High Market

{T}: Add {C}.
{T}, Sacrifice a creature: You gain 1 life.

Mind Harness

Enchant red or green creature
Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
You control enchanted creature.

Threaten

Untap target creature and gain control of it until end of turn. That creature gains haste until end of turn. (It can attack and {T} this turn.)