msem-instigator

If a creature entering the battlefield under your control causes a triggered ability of that creature to trigger, you may exile it. If you do, that ability triggers an additional time.

Vision (Whenever this or another creature you control enters, 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.

Tap up to two target creatures.
Flashback {3}{W/U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Equipped creature gets +1/+0 for each Equipment attached to it.
Equip {1}

Defender
Whenever you cast an instant or sorcery spell, you may untap Almgrove Sentinel.
{T}: Almgrove Sentinel deals 1 damage to any target.

Ancient Cairns enters tapped.
As Ancient Cairns enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{6}: Unlock Ancient Maze. If the revealed card is green, put it into your hand. Otherwise, put it on top of your library.

Trample
Morph {6} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Vigilance
If another creature would die, exile it instead.
At the beginning of your upkeep, return each creature card exiled with Arbiter of Endless Summer to the battlefield under its owner's control.

When Archivist Heretic enters, you lose 1 life, then investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Target opponent chooses a number. When they do, choose one —
• That player discards their hand, then draws cards equal to the chosen number.
• Archivist's Torment deals damage to that player equal to the chosen number.

When Arisen Haploc enters, return target creature card from a graveyard to its owner's hand.
Revive {5}{B}{B} ({5}{B}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Whenever two or more creatures an opponent controls attack, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Enchanted creatures you control get +0/+2.

Exile up to two target permanents you control, then return those cards to the battlefield under your control.

Whenever Ashen Host becomes the target of a spell, Ashen Host deals 2 damage to any target.

Enchant creature
When Aura of Leadership enters, create four 1/1 white Human Soldier creature tokens.
Enchanted creature gets +2/+2.

This spell costs {2} less to cast if a creature died under your control this turn.
Flying

Destroy target face-up creature.

Whenever Barricade Watch is dealt damage, put a +1/+1 counter on it. (It must survive the damage to get the counter.)

Enchant creature
Enchanted creature has base power and toughness 8/8.

Auras and Equipment you control have indestructible.
Whenever Bearidge Marshall attacks, you may create a white Aura enchantment token named Arrest attached to target creature. It has enchant creature and “Enchanted creature can't attack or block, and its activated abilities can't be activated.”

As an additional cost to cast this spell, remove X +1/+1 counters from among creatures you control.
Create X 2/2 green Wolf creature tokens.

Trample, haste, indestructible
Whenever a permanent an opponent controls is put into a graveyard from the battlefield, put a +1/+1 counter on target Ooze.

When Bird Call enters, search your library for a creature card, reveal it, shuffle, then put that card on top.
{2}, {T}: Target creature gets +1/+1 until end of turn.

When Blightbringer enters, creatures your opponents control get -1/-1 until end of turn.
Unearth {3}{B} ({3}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)