msem-instigator

Look at target player's hand. You may choose a nonland card from it. If you do, that player reveals that card, puts it on the bottom of their library, then draws a card.

When Improvisionist enters, if it was the second spell you cast this turn, exile the top card of your library. You may play that card until the end of your next turn.

Advance {1}{R}{R} (Cast this for {1}{R}{R} to advance it as it enters. {1}{R}{R}: Advance this as a sorcery.)
Whenever Impulse Module enters or advances, put a charge counter on it, then exile a card from the top of your library for each charge counter on it. Until your next turn, you may play one of those cards.

Enchant creature
Enchanted creature has “Whenever this creature attacks, if there are at least two other attacking creatures, this creature gains +2/+2 until end of turn.”

Target creature you control gets +2/+2 until end of turn.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

Each opponent loses 1 life and you gain 1 life. Surveil 2.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

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.

Create a tapped colorless Powercell artifact token with “{T}: Add {C}.” It doesn't untap during its controller's next untap step.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets -1/-1.
Whenever enchanted creature attacks, its controller loses 2 life.

Whenever Infernal Barrier is dealt damage, it deals 1 damage to each opponent.

When Infested Goblin dies, choose target creature. At the beginning of your next upkeep, that creature's controller sacrifices it.

Whenever Infiltrator of the Anomalous deals combat damage to a player, add {R}. Until end of turn, you don't lose this mana as steps and phases end.

Put a +1/+1 counter on target creature.
Inscribe {2}{W} ({2}{W}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Target creature gains lifelink until end of turn. Untap that creature.
Inscribe {1}{W} ({1}{W}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Draw a card.
Inscribe {1}{U} ({1}{U}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Whenever Inquisitive Guardian deals combat damage to an opponent, you may exile a nonland card from your graveyard. If you do, draw a card.
{U}: Inquisitive Guardian gains flying until end of turn.

Graft 1 (This creature enters with a +1/+1 counter on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{T}: Add {C}.

Put a +1/+1 counter on target creature. It gains indestructible until end of turn.

Search your library for a Demon card or a black card with mana value 6 or greater, reveal it, put that card in your hand, then shuffle.

Target creature you control gets +2/+2 until end of turn. If it's blocked or blocking, it gets an additional +2/+2 until end of turn.

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

When Jaakuna Bloodsworn enters, any opponent may have it deal 3 damage to them. If a player does, sacrifice Jaakuna Bloodsworn.

As long as Jadycian Empath is on the battlefield or in your graveyard, it's a land in addition to its other types.
Sacrifice Jadycian Empath: Add one mana of any color.

Menace
Jara Champion can only attack or block alone.
Whenever one or more players lose life for the first time each turn, put a +1/+1 counter on Jara Champion.

Return target creature card from your graveyard to your hand. Catalyze. (The next spell you cast this turn costs {1} less to cast.)
Flashback {3}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)