msem-instigator

When Inner-Eye Obscurist enters, return each other creature that isn't in Inner-Eye Obscurist's pack to their owners' hand. (Two or more creatures you control with equal power are in a pack.)

Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of attacking creatures.

{2}{B}, Sacrifice Innocuous Sidekick and another creature: Create a 4/4 black Horror creature token with menace. Activate only as a sorcery.

{T}: Add {U} or {R}. Spend this mana only to cast an instant, sorcery, or Wizard spell.
Whenever you cast your second spell each turn, untap Innova.

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.

Inquirer, Roaming Rover attacks each combat if able.
Whenever Inquirer deals damage to an opponent, draw a card.

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.

When Inquisitive Pod enters, draw a card.
Whenever you cast your second spell each turn, Inquisitive Pod gets +3/+3 until end of turn.

Vigilance
When Inquisitive Student enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

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.

Whenever Insatiable Abomination or another Horror you control enters, each player mills four cards.
Exile a creature card from your graveyard: Tap target Horror you control. It gains indestructible until end of turn.

Whenever Insatiable Student attacks, you may sacrifice an artifact. When you do, tap target creature an opponent controls.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets +2/+3 and has lifelink.

Whenever you cast your first instant or sorcery spell each turn, untap equipped creature.
Equip {1}

{4}, {T}: Put a -1/-1 counter on target creature.
{4}, {T}: Remove a -1/-1 counter from target creature.

Inscrutable Realms enters tapped unless you control two or more other lands.
{T}: Add {W}.
{T}, Pay 1 life: Add {G} or {U}.

Whenever a creature you control dies, Insidious Terror gets +1/+0 and gains menace until end of turn.

You may have Insipid Metamorph enter as a copy of any other creature on the battlefield, except it's 1/1.

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

Enchant creature
Enchanted creature gets +1/+2.
Whenever enchanted creature attacks, scry 1.

Flying
When Inspirational Beacon enters, you gain 3 life.