msem-instigator

Ward—Exile three cards from your graveyard. (Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player exiles three cards from their graveyard.)
Menagerie — Astralhorn Familiar gets +2/+2 as long as there are five or more creature types among creatures you control.

When Astrid, Disgruntled Princess enters, destroy target creature with mana value less than or equal to the number of Warriors you control.

Whenever equipped creature attacks, put a progress counter on Astrina, Tempered by Glory.
Equip {1}
[PROGRESS 1-2] Equipped creature gets +1/+1 and has first strike.
[PROGRESS 3+] Equipped creature gets +4/+4 and has first strike and lifelink.

Archive 3 (As this enters, shuffle the top three cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever you draw a card from the archived library, put the top card of your main library on the bottom of the archived library.
{R}: Exchange a card from the archived library with a card from your hand.

When Astute Prophet enters, draw a card. If you control a legendary creature, draw two cards instead.

When Astute Sceneweaver enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Whenever a non-Spirit creature deals combat damage to a player, destroy that creature. Its controller creates a 1/1 colorless Spirit creature token.

Once each turn, when Atal, the Shroudmaker enters or you attack with one or more Horrors, you may create two tapped 1/1 colorless Human creature tokens. If Atal isn't a token, creatures you control gain flying until end of turn.
{2}{W}{W}, Discard Atal: Create a token that's a copy of Atal, the Shroudmaker, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Whenever a nonbasic land becomes tapped or enters tapped, it doesn't untap during its controller's untap steps for as long as Ataraxia remains on the battlefield.

Whenever a land you control enters, you may pay {2}{G}. If you do, put a +1/+1 counter on Atdrik Ravager.

Vanishing 4 (This permanent enters with four time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Equipped creature gets +3/+3.
Equip {2}

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
Other creatures you control have lifelink.
Each player and cards in graveyards can't be the targets of spells or abilities your opponents control.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Whenever Atieh's Destiny or another creature you control enters, you gain 1 life and scry 1.

Flying
Whenever Atieh's Disciple attacks, scry 1.

Flying
When Atieh's Elite enters, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)
Whenever you honor a creature, until end of turn, that creature has base power and toughness 4/4, gains flying, and becomes an Angel in addition to its other types.

Flying, hexproof
At the beginning of your end step, put an exiled card with an ancestry counter on it on the bottom of its owner's library, then scry 2. If there is exactly one card exiled with an ancestry counter on it, transform Atieh.

When Atlas of Worlds enters, search your library for any number of land cards with different names and exile them, then shuffle.
You may play lands exiled with Atlas of Worlds.

When Atrocity of Flesh enters, destroy target nonland permanent.
When Atrocity of Flesh dies, you may exile it. If you do, return target card from your graveyard to your hand.

First strike (This creature deals combat damage before creatures without first strike.)
When Attended Knight enters, create a 1/1 white Soldier creature token.

Attentive Glider gets +2/+2 and has flying as long as you cast an Adventure spell or a permanent you controlled explored this turn.

Enchant creature
As long as you control an untapped creature, enchanted creature can't attack or block.

(Add a quest counter as this enters. Sacrifice after 3.)
At the beginning of your end step, if you cast no spells this turn, add a quest counter.
Untap each creature you control. Until your next turn, they gain “{T}: Scry 1.”
Scry 2, then draw two cards. You gain 2 life.

When Attuned Ancient enters, if you control a legendary creature, you may have Attuned Ancient deal damage equal to its power to target creature an opponent controls.

Haste
Augmented — When Attuned Lifeform enters, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on each creature you control. They gain vigilance until end of turn.