msem-instigator

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.)

{2}: Atieh's Acolyte gains your choice of flying, vigilance, or lifelink until end of turn.
Whenever another Angel or Nephilim you control enters, put a +1/+1 counter on Atieh's Acolyte.
Surpass {4}{W}{U} ({4}{W}{U}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

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, vigilance, lifelink
Whenever Atieh's Favored attacks, put a +1/+1 counter on each other Angel and/or Nephilim creature you control.

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.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Flash
When Atieh enters, return target noncreature spell to its owner's hand.
{W}{U}: Angel — You gain 2 life and draw a card.
{2}{W}{U}: Elder — Atieh gains “Each opponent can't cast more than one spell each turn.”

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.

Vigilance
{T}: Add one mana of any color.
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

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.)
1, 2 — At the beginning of your end step, if you cast no spells this turn, add a quest counter.
3 — 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.

Prowess
Other Monks you control get +1/+1.
Whenever you cast a spell during another player's turn, untap each Monk you control.

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Trample
Whenever Attuned Slayer deals combat damage to a player, exile that many cards from the top of your library. You may play those cards this turn.

Haste
Augmented — At the beginning of combat on your turn, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, gain control of target nonland permanent until end of turn. Untap it. It gains haste until end of turn.