Plains

Corpse Knight

Whenever another creature you control enters, each opponent loses 1 life.

Mountain

Dark Ritual

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Ashen Rider

Flying
When this creature enters or dies, exile target permanent.

Viscera Seer

Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Mortify

Swamp

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Seething Song

Bedevil

Destroy target artifact, creature, or planeswalker.

Morbid Opportunist

Whenever one or more other creatures die, draw a card. This ability triggers only once each turn.

Avatar of Discord

({B/R} can be paid with either {B} or {R}.)
Flying
When this creature enters, sacrifice it unless you discard two cards.

Despark

Exile target permanent with mana value 4 or greater.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Impulsive Pilferer

When this creature dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Encore {3}{R} ({3}{R}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Corrupted Conviction

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

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 token 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.