msem-instigator

If one or more counters would be put on a creature you control, that many plus one of each of those kinds of counters are put on that permanent instead.

Flying
When Heartless Host enters, arm target creature. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Bloodprice {U} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Counter target spell unless its controller pays {4}.

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

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.

Creature spells you cast cost {1} less to cast.

Reach

Whenever you scry, you gain 1 life for each card you looked at while scrying this way.

Haste
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Ship Vehicle becomes an artifact creature until end of turn.)

Put a +1/+1 counter on up to one target creature. Untap it. You gain 3 life.

Heat Blast deals X damage to target creature or planeswalker.

Heat Ray deals X damage to target creature.

Whenever a creature blocks, Heat of Battle deals 1 damage to that creature's controller.

Enchant creature
Prevent all damage that would be dealt by enchanted creature.
{R}, Sacrifice Heat of Day: It deals 2 damage to enchanted creature.

Until end of turn, gain control of target creature and it gains haste and shimmer. Untap it. (Whenever it attacks this turn, create a tapped and attacking token that's a copy of it. Exile that token at the beginning of the end step.)

Heated Dispute deals 3 damage to any target.
Ferocious — This spell costs {2} less to cast if you control a creature with power 4 or greater.

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

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

Flying
When Heaven's Eyes enters, create a 1/1 white Bird creature token with flying. Then you gain 1 life for each creature in Heaven's Eyes's pack. (Two or more creatures you control with equal power are in a pack.)

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.)

Flying
{T}, Tap another untapped creature in Heaven's Gale Harrier's pack: Tap target creature. (Two or more creatures you control with equal power are in a pack.)

Create a 2/2 white Angel creature token with flying.
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.)

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
Whenever this creature attacks, if it's merged with another card or token, it deals 2 damage to target player or planeswalker.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a creature you control with flying attacks, it gets +1/+1 until end of turn.