Hell Mongrel

Discard a card: Hell Mongrel gets +1/+1 until end of turn.
Madness {2}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Dark Ritual

Restless Dreams

As an additional cost to cast this spell, discard X cards.
Return X target creature cards from your graveyard to your hand.

Simian Spirit Guide

Exile Simian Spirit Guide from your hand: Add {R}.

Tortured Existence

{B}, Discard a creature card: Return target creature card from your graveyard to your hand.

Kitchen Imp

Flying, haste
Madness {B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Merfolk Looter

Hapless Researcher

Sacrifice Hapless Researcher: Draw a card, then discard a card.

Krovikan Sorcerer

{T}, Discard a nonblack card: Draw a card.
{T}, Discard a black card: Draw two cards, then discard one of them.