msem-instigator

Whenever you cast an instant or sorcery spell, look at the bottom card of your library. You may manifest it. If you don't, put it into your hand. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Put target creature on top of its owner's library.
Quickdraw {2}{U} (When a creature you control blocks or becomes blocked, you may cast this spell for {2}{U}.)

Reach
When Headhunter Mantis enters, if a creature you controlled died this turn, create a 1/1 green Insect creature token.

Heart of Carü Mapu enters tapped.
{T}: Add X mana in any combination of colors, where X is the number of basic land types among lands you control.

At the beginning of your upkeep, create a 1/1 green Saproling creature token.
Whenever a creature you control dies, put a +1/+1 counter on Heart of Spores.
{X}{G}: Move X +1/+1 counters from Heart of Spores onto target creature. Activate only as a sorcery.

Menace
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}: Another target creature you control gains menace 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.

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, lifelink

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.

Choose a nonland permanent type. Destroy all permanents of the chosen type. Each player who controlled a permanent destroyed this way draws a card.

Flying
Whenever Hecatomb Haunter enters or attacks, up to one other target nonland permanent phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

[+1]: Tap target nonland permanent. It doesn't untap during its controller's next untap step.
[–2]: Exile target tapped nonland permanent.
[–4]: Target player skips their next untap step. Tap up to three target permanents.

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, you may have it deal 3 damage to target creature if that creature's controller failed the trial.

When Heedless Lovers enters, 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.)

When this creature enters, it seeks secrets or valor. (Give it that Oath Aura. Fulfill secrets by attacking with it and two or more other creatures to draw a card. Fulfill valor by dealing combat damage to a player to create a 2/1 white Soldier token.)
Arise {3}{B}{B} ({3}{B}{B}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Disgraced 5 (This enters with five -1/-1 counters. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
Prevent all combat damage that would be dealt to Heir Unapparent.

Flying, lifelink
When Helar's Herald dies, target opponent may give themselves two poison counters. If they do, return Helar's Herald to its owner's hand. Otherwise, return Helar's Herald to the battlefield tapped under its owner's control.

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

[+2]: Until end of turn, Helene Trant becomes a 4/4 Human Warrior creature with hexproof and trample that's still a planeswalker. Prevent all damage that would be dealt to her this turn.
[–2]: Draw two cards.
[–4]: You get an emblem with “Whenever one or more creatures you control deal combat damage to a player, draw a card.”

During your turn, Helene is a 4/4 Human Warrior creature with hexproof and trample that's still a planeswalker. Prevent all damage that would be dealt to her during your turn.
[+1]: Create a green Stance enchantment token with “When a creature you control deals combat damage to an opponent, sacrifice this. If you do, draw a card.”
[–2]: Create a blue Stance enchantment token with “When an opponent casts a noncreature spell, sacrifice this. If you do, counter that spell.”

Whenever you scry, you gain life equal to the number of cards looked at while scrying this way.

Indestructible
As long as your devotion to white is less than five, Heliod isn't a creature.
If an effect would create one or more kinds of tokens under your control, it creates an additional token of each kind.
{3}{W}: Put a +1/+1 counter on each other creature you control. Activate only as a sorcery.

Choose five target cards in your graveyard. An opponent separates those cards into two piles. Put one pile into your hand and exile the other. Exile Hell or High Water.

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