msem-instigator

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.)

Deathtouch
Discard a card: Headless Carriage gains indestructible until end of turn. Tap it.
Ride {2}{B}{B} ({2}{B}{B}: Transform this and attach it to target creature you control without a Steed. Ride 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.

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

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, lifelink

You may exert Heavenly Bull as it attacks. When you do, it gains indestructible until end of turn. (An exerted creature won't untap during your next untap step.)
{3}{G}{W}: Destroy all nonland permanents with mana value 3 or less. Activate only if Heavenly Bull is attacking and only once.

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

Flying
When Helar Ritualist enters 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.

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.

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

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

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

Flash
Flying, vigilance
When Henrick enters, exile target spell. For as long as that card remains exiled, its owner may play it without paying its mana cost.
Spells players cast from anywhere but their hands cost {X} more to cast, where X is the number of creatures with flying you control.

When Herald of Darkness enters, destroy up to one target creature with mana value 3 or less.

Lifelink
When Herald of Royalty enters, creatures you control get +1/+1 and gain vigilance until end of turn.

Herald of the Yaoguai has indestructible as long as two or more creatures you control entered this turn.

Flying, prowess
Whenever one or more creatures attack, you gain life equal to the greatest power among those creatures.
Whenever you cast a white spell, you may have Heraldry become an Angel creature in addition to its other types or stop being a creature.

Beckon Ox {1}{W} ({1}{W}: This enchantment permanently becomes an Ox creature in addition to its other types.)
Vigilance
Whenever a creature or another enchantment you control enters, you gain 1 life.

When this creature enters, look at target opponent's hand. You may exile a nonland card from it. For as long as that card remains exiled, its owner may play it. A spell cast this way costs {2} more to cast.
Arise {2}{W}{W} ({2}{W}{W}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Deathtouch
Whenever a storied permanent you control enters, remove up to two counters from target creature or planeswalker an opponent controls. (Enchantments and legendary permanents are storied.)