Hideous Taskmaster

Devoid (This card has no color.)
When you cast this spell, for each opponent, gain control of up to one target creature that player controls until end of turn. Untap those creatures. They gain trample, haste, and annihilator 1 until end of turn.
Trample, haste, annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent of their choice.)

Mayhem Devil

Whenever a player sacrifices a permanent, Mayhem Devil deals 1 damage to any target.

Riveteers Ascendancy

Whenever you sacrifice a creature, you may return target creature card with lesser mana value from your graveyard to the battlefield tapped. Do this only once each turn.

Lagomos, Hand of Hatred

At the beginning of combat on your turn, create a 2/1 red Elemental creature token with trample and haste. Sacrifice it at the beginning of the next end step.
{T}: Search your library for a card, put it into your hand, then shuffle. Activate only if five or more creatures died this turn.

Ziatora, the Incinerator

Flying
At the beginning of your end step, you may sacrifice another creature. When you do, Ziatora, the Incinerator deals damage equal to that creature's power to any target and you create three Treasure tokens.

Kher Keep

{T}: Add {C}.
{1}{R}, {T}: Create a 0/1 red Kobold creature token named Kobolds of Kher Keep.

Phytotitan

When Phytotitan dies, return it to the battlefield tapped under its owner's control at the beginning of their next upkeep.