+Slave (14)
Whenever a Goblin deals combat damage to a player, that player discards a card.
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
, : Search your library for a Mercenary permanent card with mana value 5 or less, put it onto the battlefield, then shuffle.
Whenever a creature dealt damage by Dread Slaver this turn dies, return it to the battlefield under your control. That creature is a black Zombie in addition to its other colors and types.
Enchant creature
You control enchanted creature.
At the beginning of your upkeep, enchanted creature deals 1 damage to its owner.
, Sacrifice Enslaved Dwarf: Target black creature gets +1/+0 and gains first strike until end of turn.
When Enslaved Horror enters, each other player may return a creature card from their graveyard to the battlefield.
: Enslaved Scout gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)
When Grixis Slavedriver leaves the battlefield, create a 2/2 black Zombie creature token.
Unearth (: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)
, , Sacrifice Kindslaver: A person outside the game controls target player during that player's next turn. Neither player may advise that person until the end of that turn.
, , Sacrifice Mindslaver: You control target player during that player's next turn. (You see all cards that player could see and make all decisions for the player.)
When Raving Oni-Slave enters or leaves the battlefield, you lose 3 life if you don't control a Demon.
Gain control of target creature. Untap that creature. It gains haste until end of turn. Sacrifice it at the beginning of the next end step.
Trample
Forestcycling (, Discard this card: Search your library for a Forest card, reveal it, put it into your hand, then shuffle.)
Whenever Slavering Nulls deals combat damage to a player, if you control a Swamp, you may have that player discard a card.
Gatherer works better in the Companion app!
, 
: Search your library for a Mercenary permanent card with mana value 5 or less, put it onto the battlefield, then shuffle.