Corpse Knight

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

Counterspell

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Bitterblossom

At the beginning of your upkeep, you lose 1 life and create a 1/1 black Faerie Rogue creature token with flying.

Arcane Sanctum

Arcane Sanctum enters tapped.
{T}: Add {W}, {U}, or {B}.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Nevinyrral, Urborg Tyrant

Hexproof from artifacts, creatures, and enchantments
When Nevinyrral, Urborg Tyrant enters, create a tapped 2/2 black Zombie creature token for each creature that died this turn.
When Nevinyrral dies, you may pay {1}. When you do, destroy all artifacts, creatures, and enchantments.

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.