Duskmourn: House of Horror Commander

Instant — Arcane

Return target legendary creature card from your graveyard to the battlefield. That creature gains haste. Exile it at the beginning of the next end step.
Splice onto Arcane {2}{B} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Goryo's Vengeance

Secret Lair Countdown

Sorcery

Target creature you control gets +X/+X until end of turn. Then it fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)

Primal Might

Secret Lair Drop

Instant

({B/P} can be paid with either {B} or 2 life.)
Target creature gets -5/-5 until end of turn.

Dismember

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Blasphemous Act

Beast

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Artifact

Creature cards in graveyards and libraries can't enter the battlefield.
Players can't cast spells from graveyards or libraries.