msem-instigator

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.)

Flying
When Ineptitude enters, untap target creature and gain control of it until end of turn. Put three stun counters on that creature. It gets +3/+3 and gains haste until end of turn.

Target creature gets -1/-1 until end of turn.
Threshold — You may destroy that creature instead if seven or more cards are in your graveyard.

This spell costs {1} less to cast for each creature and/or planeswalker card in your graveyard.
Return target creature or planeswalker card from your graveyard to the battlefield.

When Infamous Bilgecaptain enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.)
Other Pirates you control get +1/+1.
At the beginning of your end step, you may put a Pirate card with mana value less than or equal to the number of artifacts you control from your hand onto the battlefield.

Lifelink
Whenever Infectious Ego enters or attacks, exile the top card of target opponent's library. If it's a land card, that player gets a poison counter. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.

Menace
Ward—Pay 3 life.
When Infernal Direwolf enters, it fights up to one target creature an opponent controls. Excess damage Infernal Direwolf deals this way is dealt to that creature's controller instead.

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.

Enchant creature
Enchanted creature has “{R}, {T}: Create an X/1 red Elemental creature token with haste and trample, where X is this creature's power. Exile that token at the beginning of the next end step.”

Inferno Lash deals 2 damage to target creature or planeswalker. When it does, torment that permanent's controller. (They lose 3 life unless they discard a card or sacrifice a nonland permanent.)

Search target player's library for a card and exile it. Then that player shuffles.

Each opponent plays with the top card of their library revealed.
During each of your turns, you may play one card from the top of an opponents' library, and you may spend mana as though it were mana of any color to cast that spell.

Once each turn, when a player casts a spell, you may choose two target players. Each of those players exiles cards from the top of their library until they exile a nonland card with mana value less than that spell's. They may cast those cards without paying their mana cost. Then they put the rest of the exiled cards on the bottom of their library in a random order. (The active player puts their spell on the stack first.)

{3}, {T}: Put Ing'Wei's Crystal Top on top of your library. Scry 3, then draw a card.

Flying, prowess
Whenever you cast a noncreature spell, untap Ingenious Trickster.

Gain control of target creature if its power is less than or equal to the number of counters on creatures you control.

Whenever Inkwell Daggers enters or attacks, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

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 a creature you control enters for the second time each turn, it gains haste until end of turn. You may have it get +1/+1 until end of turn.

{T}, Sacrifice a land: Destroy target land.

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}.

[+1]: Each opponent puts a -1/-1 counter on a creature they control.
[–1]: Exile target card in a graveyard. You gain life equal to its mana value.
[–6]: Choose a number. You draw that many cards and you lose that much life.

{3}{B}, {T}: Choose a card name. Target player reveals cards from the top of their library until they reveal a card with the chosen name. If they do, put the revealed cards into their graveyard. Otherwise, they shuffle their library.

Inquisitor's Chamber enters tapped.
{T}: Add {B}.
{B}{B}, {T}, Sacrifice another permanent: Draw a card.