Awaken the Blood Avatar

As an additional cost to cast this spell, you may sacrifice any number of creatures. This spell costs {2} less to cast for each creature sacrificed this way.
Each opponent sacrifices a creature of their choice. Create a 3/6 black and red Avatar creature token with haste and "Whenever this creature attacks, it deals 3 damage to each opponent."

Extus, Oriq Overlord

Double strike
Magecraft — Whenever you cast or copy an instant or sorcery spell, return target nonlegendary creature card from your graveyard to your hand.

Extus, Oriq Overlord // Awaken the Blood Avatar

Soot Imp

Flying
Whenever a player casts a nonblack spell, that player loses 1 life.

Eidolon of Rhetoric

Each player can't cast more than one spell each turn.

Spirit of the Labyrinth

Each player can't draw more than one card each turn.

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, Eidolon of the Great Revel deals 2 damage to that player.

Magebane Lizard

Whenever a player casts a noncreature spell, Magebane Lizard deals damage to that player equal to the number of noncreature spells they've cast this turn.

Dauntless Dismantler

Artifacts your opponents control enter tapped.
{X}{X}{W}, Sacrifice Dauntless Dismantler: Destroy each artifact with mana value X.

Rug of Smothering

Flying
Whenever a player casts a spell, they lose 1 life for each spell they've cast this turn.

Archon of Emeria

Flying
Each player can't cast more than one spell each turn.
Nonbasic lands your opponents control enter tapped.