msem-instigator

When Cyone, Expedition Captain enters, create a 1/1 Scout creature token that's all colors, then choose flying, first strike, or lifelink. Creature tokens you control gain the chosen ability until end of turn.
Whenever Cyone attacks, aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

Creature spells you cast cost {2} less to cast.
Whenever another nontoken creature you control enters, it becomes a colorless Vehicle artifact with crew 1. (Tap any number of creatures you control with total power 1 or greater: That Vehicle becomes an artifact creature until end of turn.)

Flying
Whenever DC-4 Cutie enters or attacks, choose target creature card with mana value 3 or less in your graveyard. You may cast it this turn.
Crew 2

Vigilance, reach
When DL-19 Reject enters, target creature you control gets +2/+2 until end of turn.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature an opponent controls dies, create a Food token. (It's an artifact with “{2}, {T}, Sacrifice this artifact: You gain 3 life.”)

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
{3}{G}: Da'Lang gets +2/+2 until end of turn. If you're in a renaissance, all creatures able to block Da'Lang this turn do so. Activate only once each turn.

Adorned — Daelish Archer has first strike as long as it's equipped and/or enchanted.

Flying (This creature can't be blocked except by creatures with flying or reach.)

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
Whenever you cast a spell, Daemonspawn deals 1 damage to each cursed opponent.

Daggersworn Elite enters tapped.
Whenever Daggersworn Elite and at least two other creatures attack, you may pay {1}{B}. If you do, destroy target tapped creature.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
When Dai Gui enters, create a 1/1 green and blue Bird creature token with flying and “{T}: Add one mana of any color.”
{X}{X}{G}{U}: Demigod — You gain X life and you draw X cards. X can't be 0.
{X}{X}{G}{U}: God — Put up to X creature cards from your hand onto the battlefield.

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Frontiers Anew {G}
Sorcery — Adventure
Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Then exile this card. You may cast the creature later from exile.)

Other creatures you control get +1/+1 as long as you control four or more lands.
{G}, Sacrifice Daisy, the Heart of Chasmek: Creatures you control with base power 1 or less gain indestructible until end of turn.

Whenever a creature an opponent controls becomes blocked, put a -1/-1 counter on that creature.

First strike
Noncreature spells cost {1} more to cast as long as their controller is horrific. (A player is horrific as long as they've sacrificed a permanent or discarded a card this turn.)

{1}: Danaj Sightseer gains lifelink until end of turn if {W} was spent to activate this ability. The same is true for flying and {U}, menace and {B}, first strike and {R}, and trample and {G}.
At the beginning of your end step, if you've spent {W}{U}{B}{R}{G} to cast spells and/or activate abilities this turn, put three +1/+1 counters on Danaj Sightseer.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
When Dancer of the Great Current enters, tap up to one target creature. If you control two or more other creatures that are Merfolk, Wizards, or Rogues, instead return that creature to its owner's hand and put a +1/+1 counter on Dancer of the Great Current.

{B}, Sacrifice another creature: Exile target card in an opponent's graveyard. You may cast that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell. Activate only as a sorcery.

{T}, Discard a card, Sacrifice Danithra Oracle: Target creature gets -3/-3 until end of turn. Activate only as a sorcery.

Vigilance
Whenever Danuri Banisher deals combat damage to a player, you may exile target creature. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.

Identity — When Danuri Warcaller enters, if you control at least two other creatures that share a creature type with it, create a 1/1 white Soldier creature token.

Whenever another creature in Daoshi Spiritdancer's pack dies, you may sacrifice Daoshi Spiritdancer. If you do, return that creature card to the battlefield under your control at the beginning of the next end step. (Two or more creatures you control with equal power are in a pack.)

Trample
Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)

Whenever Daring Skythief crews a Vehicle, that Vehicle gains flying until end of turn.

Flying
Whenever you gain life, target creature an opponent controls gets -1/-1 until end of turn.