msem-instigator

First strike
{1}{R}: Hatsuo, Honored General and other Warrior creatures you control get +1/+0 until end of turn.

When Haughty Paladin enters the battlefield, you may sacrifice another artifact or creature. If you do, tap all creatures your opponents control.

When Haunted Heirloom dies, create a Treasure token.

{W}, Sacrifice Haunting Bard: Destroy target artifact or enchantment.

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

Scavenge {5}{U} ({5}{U}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

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

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

Reach

Vigilance
{W}: Heaven's Champion gains first strike until end of turn.

Flying
When Heaven's End Chronicler enters the battlefield, mill three cards, then choose three cards in your graveyard. An opponent separates them into two piles. Return one pile to your hand.

Whenever a creature in Heaven's Fire Ascetic's pack attacks, that creature deals 1 damage to defending player. (Two or more creatures you control with equal power are in a pack.)

Trial 3 (As you cast this spell, an opponent of your choice may pay 3 life. If they don't, they fail the trial.)
When Heedless Adversary enters the battlefield, you may have it deal 3 damage to target creature if that creature's controller failed the trial.

When Heedless Lovers enters the battlefield, you may return target Citizen card from your graveyard to your hand.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

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 the battlefield.)

When Heirloom Seeker enters the battlefield, you may search your library for an Equipment card, reveal it, then shuffle your library and put that card on top of it.
Heirloom Seeker has first strike as long as it's equipped.

Flying
When Helar Ritualist enters the battlefield or whenever you cast a spell, if {W}{B} was spent to cast it, each opponent loses 3 life and you gain 3 life. Put a +1/+1 counter on Helar Ritualist.

At the beginning of each combat, up to one target creature can't attack or block this turn.

Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)
Other creatures you control have infiltrate.

When Helicos Aberration enters the battlefield, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Flying, lifelink, haste
At the beginning of the end step, sacrifice Helix Entity.

This spell costs {X} less to cast, where X is your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)
Trample

Menace
{1}{B}{R}: Creatures you control get +1/+0 until end of turn.

When Hellion Devastator enters the battlefield, destroy up to one target nonland permanent with mana value 3 or less.
Cycling {2} ({2}, Discard this card: Draw a card.)

Haste
The first instant or sorcery spell you cast each turn costs {1} less to cast.
{R}, {T}, Sacrifice Hellspark Prankster: Change the target of target spell with a single target.