msem-instigator

Whenever a land enters the battlefield under your control, put a +1/+1 counter on target creature you control.

Whenever a creature you control deals combat damage to a player, if it has no +1/+1 counters on it, put a +1/+1 counter on it. You gain 1 life.

Harmony — Search your library for a basic land or Desert card, reveal it, and put it into your hand. Then shuffle.
When Trumpeting Pathmaker enters the battlefield, harmonize. (Trigger up to one harmony of a permanent you control.)

Vigilance
Assault {G} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)

(Transform this if it's not attached to a creature. Pay {2}{W} as a sorcery to unattach it.)
Enchant creature you control
Trusty Steed's rider gets +2/+2.

Flash
Enchant artifact or creature
Enchanted permanent is an artifact with “{T}: Draw a card then discard a card” and loses all other card types and abilities.

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)
When Tutorial Boss enters the battlefield, create a 1/1 blue Pirate creature token.

Double strike
Ride {2}{W} ({2}{W}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Double strike
Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Engage (This creature must be blocked each combat if able.)

At the beginning of your upkeep, exile the top card of your library. You may play it this turn. Whenever you cast an instant or sorcery spell exiled this way, you may copy it and you may choose new targets for the copy.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
I, II — Each opponent loses 2 life and you gain 2 life.
Discovery — At the beginning of your end step, you draw a card and you lose 2 life.

This spell costs {1} less to cast for each foretold card you own in exile, each permanent you control with foretell, and each card with foretell in your graveyard.
Flying
When Tyrant of Prophecies enters the battlefield, it deals 3 damage to any target.

Whenever Ujuraq, Elder Watcher enters the battlefield or attacks, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
Ujuraq gets +3/+3 and has trample as long as there are eight or more cards in your graveyard.

Assault {X}{R}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Other Elementals you control get +1/+0.
When Unbound Annihilus assaults, create X 1/1 red Elemental creature tokens that are tapped and attacking.

At the beginning of each opponent's upkeep, that player may discard their hand. If the player does, sacrifice Under the Gun. Otherwise, put a bullet counter on Under the Gun, then that player loses life equal to the number of bullet counters on it.

Bleed {1}{B} (You may cast this spell for its bleed cost if an opponent lost life this turn.)
When Undermurk Scavenger enters the battlefield, you draw a card and you lose 1 life.

Vigilance
Whenever Underpass Sentinel enters the battlefield or attacks, you may put a +1/+1 counter on another target creature you control without one.
Sacrifice Underpass Sentinel: Embattled creatures you control gain hexproof and indestructible until end of turn. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Target creature can't block until end of turn. If that creature had a Steed attached to it, unattach that Steed and it can't block until end of turn.
Draw a card.

Until end of turn, you can't lose the game, your opponents can't win the game, and your life total can't change.

When United in Battle enters the battlefield, look at the top six cards of your library. You may reveal a Dwarf or Elf card from among them and put it into your hand. Put the rest on the bottom in a random order.
Whenever a Dwarf or Elf enters the battlefield under your control, put a +1/+1 counter on it.

Glitch—Sacrifice a creature. (Remove one [restriction] for each time you pay the glitch cost.)
When Unshackled Revolutionary enters the battlefield, you may destroy target creature an opponent controls [with mana value 3 or less]. [You lose 3 life.]

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Exile target nonland permanent an opponent controls. If this spell was harnessed by a token, you gain 5 life.

When Urn of Heroes enters the battlefield, you may search your library for a legendary card, put that card into your graveyard, then shuffle.
{T}: Add {C}.

Haste
When Urud Stingswoop enters the battlefield, it gains flying until end of turn.