msem-instigator

When Harried Submersible enters, target opponent creates a 1/1 blue Tentacle creature token.
Whenever Harried Submersible deals combat damage to a player or planeswalker, draw a card.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Flying
Harrier's Falcon can't attack or block alone.

As an additional cost to cast this spell, sacrifice a permanent.
When Harriet, Liberated Wildborn enters, you may remove all counters from target permanent.

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Wanderlust — When you cast this spell, you may copy it if you control four or more differently named lands. You may choose new targets for the copy.
Target creature you don't control gets -3/-3 until end of turn.

Target creature gets +3/-1 until end of turn.
Metamorph {1}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up and cast it at any time for its metamorph cost.)

Sacrifice a creature: Harrowing Knight gets +2/+2 until end of turn.

Destroy target colorless nonbasic permanent. Harsh Erosion deals 2 damage to that permanent's controller.

Enchant creature
Enchanted creature gets +2/+0 and has haste.

Harsh Wastes deals 3 damage to target attacking or blocking creature.

When Harshapal Banner enters, create three 1/1 white Soldier creature tokens with vigilance.
Equipped creature gets +2/+2.
Equip {3}

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.

Creatures with defender you control can attack as though they didn't have defender.
Each creature you control assigns combat damage equal to its toughness rather than its power.

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.”

Cast this spell only during your turn and only during the declare attackers step or with its acquiesce ability.
Untap all creatures you control. After this phase, there is an additional combat phase.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Enchant land
Whenever enchanted land is tapped for mana, its controller adds one mana of any color.

When a creature scavenges Harvest Reaper, search your library for a colorless card, reveal it, put it into your hand, then shuffle.
Scavenge {2} ({2}, 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.)

At the beginning of your upkeep, Harvest the Stars deals 4 damage to any target.

Whenever Harvester of Secrets or another creature enters from your graveyard, you may draw a card.
Unearth {2}{U}{B} ({2}{U}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

Harvest (You may tap any number of creatures you control as you cast this spell. If you do, reduce this spell's mana cost by their total power.)
Create a 5/5 colorless Scarecrow artifact creature token with “This creature can't block or harvest.”
Flashback {8}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Whenever you cast an instant or sorcery spell from your hand, put that card onto the battlefield face down as a 2/2 creature instead of putting it into your graveyard as it resolves.
Whenever a face-down creature you control deals combat damage to an opponent, you may exile it. If you do, you may cast it without paying its mana cost.

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.

Discard your hand. Creatures you control get +X/+0 and gain first strike until end of turn, where X is the number of cards discarded this way.