msem-instigator

Elemental, instant, and sorcery spells you cast cost {1} less to cast.

Flying, haste
Whenever you attack with three or more creatures, harmonize three times. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may instead return Herald of Festivities from your graveyard to your hand.

Flying
Whenever Herald of Flame attacks, gain control of target permanent until end of combat. If it's a creature, you may have it become tapped and attacking.
Whenever a creature you control becomes blocked, Herald of Flame deals 3 damage to the player or planeswalker that creature is attacking.

Haste
{1}{R}, {T}: Attacking creatures you control get +1/+0 until end of turn.

Haste
Whenever Herald of the Humble deals combat damage to a player, that player reveals the top card of their library. If it's a nonland card with mana value 3 or less, they may cast it without paying its mana cost.

Target opponent may draw two cards. If they do, you draw four cards. Otherwise, you create four 1/1 red Elemental creature tokens.

Whenever Hero of Aer attacks, it gets +2/+1 until end of turn.

Equipped creature gets +3/+1 and has haste.
Equip Soldier or Warrior {1}
Equip {4}

Scry 2, then create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Monument {2}{R} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Hidden Prowess deals 2 damage to target creature. When that creature dies this turn, create a 1/1 red Elemental creature token.

Prowess
Whenever High Rollers Croupier attacks, you may put a lore counter on a Saga you control.

Flash
Prowess
When High Rollers Esteemed enters, you may choose new targets for target spell or ability unless its controller has High Rollers Esteemed deal 4 damage to them.

When Highbeam Hulk enters, you may discard a card. If you do, draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

({T}: Add {R}.)
As Highland Dunes enters, you may pay 1 life. If you don't, Highland Dunes enters tapped.

{2}{R}, {T}, Exert Hinterland Ritualist, Sacrifice another creature: Hinterland Ritualist deals damage equal to the sacrificed creature's power to any target. Activate only as a sorcery. (An exerted creature won't untap during your next untap step.)

Flying
When Hoarding Dragon enters, you may search your library for an artifact card, exile it, then shuffle.
When Hoarding Dragon dies, you may put the exiled card into its owner's hand.

When Hollow Hooligan enters, up to two target creatures can't block this turn.
Mirage {1}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Trample, haste

Double strike
When a creature scavenges Hook-Style Trainee, put a double strike counter on that creature.
Scavenge {4}{R} ({4}{R}, 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.)

Other Pirates you control get +1/+0.
Whenever another Pirate you control enters, Hookhand Freebooter deals 1 damage to any target.
When Hookhand Freebooter dies, create a Bullet token. (It's an artifact with “{T}, Sacrifice this artifact: It deals 1 damage to any target.)

Armed — Whenever Hordedriver Enthusiast attacks, if it's equipped, creatures you control get +1/+0 and gain trample until end of turn.

Flying, haste
At the beginning of each of your postcombat main phases, you may cast an instant or sorcery card from your graveyard with mana value less than or equal to the number of creatures that dealt combat damage to opponents this turn without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Haste
When Horse Thief enters, you may gain control of target creature or Steed until end of turn. It gains haste until end of turn. If it's a Steed, attach it to Horse Thief.

Tap an untapped Desert you control: Hostile Atmosphere deals 1 damage to any target.

Hostile Habitat deals 2 damage to each creature.
Leitmotif (If you cast this spell from your hand, exile it as it resolves. When you next cast a spell that shares a color with this card, you may cast this from exile without paying its mana cost.)