msem-instigator

Flying
Whenever Aether Crosser attacks, you may aetherize another target tapped creature you control. (To aetherize, create a token that's a copy of it, then exile that token.)
Crew 1

{T}, Sacrifice Aether Gateway: Create a tapped Plains token, Island token, Swamp token, Mountain token, or Forest token.

Vision (Whenever this or another creature enters the battlefield under your control, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Aether Recoverer envisions a creature card, return target noncreature card from your graveyard to your hand.

If a creature dealt damage by equipped creature this turn would die, exile that card and draw a card instead.
Equip {1}

You control equipped creature.
Equipped creature has hexproof and can't attack or block.
{3}: Attach Aetherite Shackles to target creature. Activate only as a sorcery.

Defender, reach
Aetherlock Effigy can block an additional creature each combat.
When Aetherlock Effigy dies, create two 1/1 black Bird creature tokens with flying.

Equipped creature gets +1/+0 and has first strike.
{1}{R}: Equipped creature gets +1/+0 until end of turn.
Equip {2}

Equipped creature gets +2/+1.
Equip multicolored creature {1}
Equip {2}

Target creature you control fights target creature you don't control. You may discard a card. If you do, draw a card.

When Ageless Ascetic enters the battlefield, return up to one target instant or sorcery card from your graveyard to your hand.

Flying
When Ageless Lorekeeper enters the battlefield, you may discard your hand. When you do, draw three cards.

Whenever a land enters the battlefield under your control, untap Ageless Wanderer.
{1}, {T}: Add one mana of any color.

When Ageless Weaver enters the battlefield, create a green Aura enchantment token named Years of Experience attached to target creature. The token has enchant creature and “Enchanted creature gets +2/+2.”
Whenever an enchanted creature you control dies, create a 3/3 green Elemental creature token.

Whenever Agent of Vitu-Ghazi deals combat damage to a player, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Target creature you control deals damage equal to its power to target creature you don't control.

Menace, trample, indestructible
Whenever Aghavaan Unleashed deals combat damage to a player, that player gets that many poison counters.
At the beginning of your end step, sacrifice another creature or transform Aghavaan Unleashed.

Poisonous 1 (Whenever this creature deals combat damage to a player, that player gets a poison counter.)
At the beginning of your upkeep, destroy target artifact or enchantment if its controller is poisoned.

{T}: Add {C}.
At the beginning of each end step, if you control five or more Snake creatures, transform Aghavaan's Wound.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
I, II — Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Discovery — {4}: You gain 2 life.

{T}, Discard a card: Add {C}.
Whenever you discard one or more cards, you may pay {2}. If you do, draw a card.

Enchant land
When Aid from Martoob enters the battlefield, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)
When enchanted land is tapped for mana, add one mana of any color.

Cast this spell only if creatures you control have a total power of 10 or greater or you control six or more lands.
Create two 6/6 green and white Elk creature tokens.

[+1]: Aiel Tazan deals 2 damage to any target. Then she deals 2 damage to herself unless you have her deal 2 damage to you.
[–3]: Creatures you control get +2/+0 and gain haste until end of turn.
[–X]: Create an X/1 red Elemental creature token with haste and trample. Exile that token at the beginning of the next end step. If X is 6 or more, it gains double strike.

Menace, haste
Whenever Aiel's Fury attacks, scry 2, then reveal the top card of your library. Aiel's Fury gets +X/+0 until end of turn, where X is that card's mana value.

Ainok Alpha can't be blocked by more than one creature.
Other Hounds you control get +1/+1 and can't be blocked by more than one creature.