Homicidal Seclusion

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

Demon

Unhallowed Pact

Enchant creature
When enchanted creature dies, return that card to the battlefield under your control.

Crippling Chill

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

Into the Void

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

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.

Swamp

Island

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.)

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.

Doom Blade

Flight

Enchant creature
Enchanted creature has flying.

Mist Raven

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

Nephalia Smuggler

{3}{U}, {T}: Exile another target creature you control, then return that card to the battlefield under your control.

Drudge Skeletons

{B}: Regenerate Drudge Skeletons. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Marrow Bats

Flying
Pay 4 life: Regenerate Marrow Bats.

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.

Alchemist's Apprentice

Sacrifice Alchemist's Apprentice: Draw a card.

Essence Harvest

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

Peel from Reality

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

Mind Control

Enchant creature
You control enchanted creature.

Bonds of Quicksilver

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Counterspell

Crypt Creeper

Sacrifice Crypt Creeper: Exile target card from a graveyard.

Renegade Demon

Liliana of the Veil

+1: Each player discards a card.
−2: Target player sacrifices a creature.
−6: Separate all permanents target player controls into two piles. That player sacrifices all permanents in the pile of their choice.

Tormentor's Trident

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

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.)

Frost Breath

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

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.

Fettergeist

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

Levitation

Undead Executioner

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

Cancel

Havengul Skaab

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