msem-instigator

Spells and abilities you control that target Inconspicuous Sheep cost {1} less.
As long as Inconspicuous Sheep is enchanted or equipped, they're a 3/3 legendary Sheep Rogue named Agent S.

As a permanent you control explores an Aura, you may put it onto the battlefield attached to Inconspicuous Stowaway.
As long as Inconspicuous Stowaway is enchanted or equipped, she's a legendary 2/3 Cat Rogue named Agent C and has double strike.

Creatures you control attacking causes their death knell to trigger.
Death knell — Indomitable Spirit gets +2/+2 and gains trample until end of turn. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

Enchant creature
At the beginning of combat on your turn, create a token that's a copy of enchanted creature, except it has haste. Exile that token at the beginning of the next end step.

{T}: Add one mana of any color.
Whenever you tap Ingrained Virago for mana, each opponent loses 1 life.

Mill three cards, then you may return a creature or land card from your graveyard to your hand.

{1}{W}, {T}: Tap target creature.
Put a -1/-1 counter on Insistent Ingenue: Untap Insistent Ingenue.

Destroy target land. Into the Maw of Hell deals 13 damage to target creature.

Advance {4}{R} (Cast this for {4}{R} to advance it as it enters. {4}{R}: Advance this as a sorcery.)
Whenever Intruder Drone advances, exile the top card of your library. You may cast a spell exiled with Intruder Drone with mana value 3 or less without paying its mana cost.

Untap all creatures you control.
Draw a card.

Codex — Little Pig; Charging Cassowary; The Lonely Hunter; Shadowlurk; Blood Constrictor. (As this enters, conjure its contents into a shuffled face-up additional library.)
You may cast Adventures of this codex's contents from your graveyard.

Target creature you control deals damage equal to its power to another target creature.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Flash
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Advance {2} (Cast this for {2} to advance it as it enters. {2}: Advance this as a sorcery.)
Equipped creature gets +X/+0 and has flying, where X is the number of times it and Jet Pack have advanced this turn.
Equip {1}

Destroy target permanent. Trigger a death knell of any number of permanents you control.

Return target creature card from your graveyard to your hand. (Then exile this card. You may cast the creature later from exile.)

Codex — Hannah, Aethertechnician; Flynn Skara; Pidge, Tinkering Courier; Reyhsia, Truth Chaser. (As this enters, conjure its contents into a shuffled face-up additional library.)
You may spend mana as thought it were mana of any color to cast this codex's contents.
Sacrifice Karina's Connections: Copy target activated ability of one of its contents. You may choose new targets for the copy.

Whenever you make first contact, you may activate one of Karina's loyalty abilities. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)
[+1]: Each player draws a card.
[–2]: Exile target nonland permanent. At the beginning of the next end step, return it to its owner's hand or to the battlefield under its owner's control.
[–7]: You get an emblem with “You may cast spells that don't have the same name as a permanent you control or a card in your graveyard without paying their mana costs.”

Vigilance
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Flash
Flying
When Laughing Bird enters, you may return a creature you control to its owner's hand.

Lava Plume deals 3 damage to any target.
At the beginning of each end step, if you have 5 or less life, you may pay {R} and exile Lava Plume from your graveyard. If you do, it deals 3 damage to any target.

Flash
When Leafcrowned Fox enters, return to your hand target creature card from your graveyard that was put there from anywhere this turn. If it has mana value 3 or less, you may return it to the battlefield under your control instead.

As an additional cost to cast this spell, exile a card from your graveyard.
Counter target spell with mana value less than or equal to the exiled card's mana value.

{T}: Exile two target creature and/or land cards from a graveyard. Create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
{B}{G}, Sacrifice two Vials: Sacrifice Leticia Petrine, then return her to the battlefield transformed under her owner's control.

When Life from Death enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Whenever a nontoken creature you control dies, create a 1/1 green Saproling creature token.