msem-instigator

Hartwin, Cunning Lieutenant can't block.
If spell or ability would cause an opponent to discard a card, instead that player discards a card at random. When a nonland card with mana value 2 or less is discarded this way, you may cast it without paying its mana cost.

When Harvest Blighter enters, create a black Aura Curse enchantment token named Rotting Away attached to target player. The token has enchant player and “Whenever a creature enters under enchanted player's control, if it has toughness 2 or greater, put a -1/-1 counter on that creature.”

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature enters under an opponent's control, you may have that player lose 1 life.

Menace
Art of war — At the beginning of your end step, if Hashiro's Infiltrator dealt damage to an opponent this turn, that player discards a card.

When Hashiro's Vanguard enters, each player sacrifices a nontoken creature.

Target player discards two cards and loses 2 life. Scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Lifelink
Whenever you sacrifice a creature, you gain life equal to its power.

Flying
Whenever Haunting Horseman deals combat damage to a player, that player discards a card.

Enchant creature
Enchanted creature gets -1/-3.

Flying, lifelink

Deathtouch
Discard a card: Headless Carriage gains indestructible until end of turn. Tap it.
Ride {2}{B}{B} ({2}{B}{B}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Menace
When Heart of the Deadwood enters, destroy up to one target creature, then put up to one target creature card from a graveyard onto the battlefield under your control.

At the beginning of your upkeep, if you have less life than an opponent, you lose 1 life and you draw a card.

Menace
Sacrifice a Goblin: Heartless Warleader gets +2/+2 until end of turn.

Deathtouch
Whenever another creature dies, its controller discards a card at random.

Kicker {2}{B} (You may pay an additional {2}{B} as you cast this spell.)
Flying
When Heartstabber Mosquito enters, if it was kicked, destroy target creature.

Enchant creature
When Heartstrings leaves the battlefield, exile enchanted creature.
Whenever enchanted creature attacks or blocks, exile it at end of combat.

Lifelink
Embellish {2}{B} (If you cast this spell for {2}{B}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)

This spell costs {2} less to cast if you sacrificed a Clue this turn.
Target player discards two cards.

Whenever you cast a spell with two or more black mana symbols in its mana cost, you draw a card and you lose 1 life.

When Helicos-Drowned Captain enters, create a black Aura Curse enchantment token named Marked for Death attached to target player. The token has enchant player and “At the beginning of enchanted player's upkeep, that player loses 1 life.”

Whenever you lose 2 or more life during your turn, put two blood counters on Hemomancy.
{1}{B}, Remove X blood counters from Hemomancy: Return target creature card with mana value X from your graveyard to the battlefield.

Lifelink

Pressure {2}{B} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)
Menace (This creature can't be blocked except by two or more creatures.)

When Herald of Darkness enters, destroy up to one target creature with mana value 3 or less.