Corpse Traders

{2}{B}, Sacrifice a creature: Target opponent reveals their hand. You choose a card from it. That player discards that card. Activate only as a sorcery.

Lone Revenant

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever Lone Revenant deals combat damage to a player, if you control no other creatures, look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Peel from Reality

Return target creature you control and target creature you don't control to their owners' hands.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Homicidal Seclusion

As long as you control exactly one creature, that creature gets +3/+1 and has lifelink.

Mist Raven

Flying
When Mist Raven enters, return target creature to its owner's hand.

Undead Executioner

When Undead Executioner dies, you may have target creature get -2/-2 until end of turn.

Crippling Chill

Tap target creature. It doesn't untap during its controller's next untap step.
Draw a card.

Alchemist's Apprentice

Sacrifice Alchemist's Apprentice: Draw a card.

Island

Havengul Skaab

Whenever Havengul Skaab attacks, return another creature you control to its owner's hand.

Crypt Creeper

Sacrifice Crypt Creeper: Exile target card from a graveyard.

Swamp

Essence Harvest

Target player loses X life and you gain X life, where X is the greatest power among creatures you control.

Renegade Demon

Triumph of Cruelty

At the beginning of your upkeep, target opponent discards a card if you control the creature with the greatest power or tied for the greatest power.

Doom Blade

Frost Breath

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Demonic Rising

At the beginning of your end step, if you control exactly one creature, create a 5/5 black Demon creature token with flying.

Marrow Bats

Flying
Pay 4 life: Regenerate Marrow Bats.

Tormentor's Trident

Equipped creature gets +3/+0 and attacks each combat if able.
Equip {3}

Into the Void

Return up to two target creatures to their owners' hands.

Fettergeist

Flying
At the beginning of your upkeep, sacrifice Fettergeist unless you pay {1} for each other creature you control.

Predator's Gambit

Enchant creature
Enchanted creature gets +2/+1.
Enchanted creature has intimidate as long as its controller controls no other creatures. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)