msem-instigator

Whenever Imisti, Elven Insurgent attacks, mill two cards. When you do, you may return target land card from your graveyard to your hand.
{X}{B}{G}: If Imisti has no +1/+1 counters on it, put X +1/+1 counters on Imisti. Activate only as a sorcery.

Imitator of Drakes has flying as long as it has a +1/+1 counter on it.
{2}{U}: Put a +1/+1 counter on Imitator of Drakes.

At the beginning of each opponent's end step, that player gets a poison counter unless damage was dealt this turn.

Indestructible
Immortal Child can't block creatures with greater power.

Defender
When Immured Fiend enters, target opponent discards two cards.

First strike, vigilance
Partner with Commander Hyctaleon (When this creature enters, target player may put Commander Hyctaleon into their hand from their library, then shuffle.)
At the beginning of your upkeep, you may search your library for a Soldier card, reveal it, put it into your hand, then shuffle.

When Imperial Artisan enters, draw three cards, then put two cards from your hand on top of your library in any order.

Haste
Whenever a nonbasic land becomes untapped, its controller loses 1 life.

Trample
If a creature in Imperial Guardian's pack would deal damage to a permanent or player, it deals twice that much damage instead. (Two or more creatures you control with equal power are in a pack.)

First strike
Art of war — At the beginning of your end step, if Imperial Kensai dealt damage to an opponent this turn, you may pay 1 life. If you do, put a +1/+1 counter on Imperial Kensai.

Trample
Art of war — At the beginning of your end step, if Imperial Legion dealt damage to an opponent this turn, put two +1/+1 counters on it.

As long as Imperial Proclaimer is on the battlefield, it has all names of nonlegendary creature cards in addition to its name.

Flash
You may cast this spell from your graveyard, but not from anywhere else. When you do, destroy target permanent.

Lionize {1}{U} ({1}{U}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following ability until end of turn. You may cast this card on a later turn from exile.)
Hexproof

{1}, Sacrifice a creature: Put a +1/+1 counter on Implant Scavenger and move any +1/+1 counters from the sacrificed creature onto it. It gains menace until end of turn.

Reach
{1}, Sacrifice a nonland permanent: Imposing Manticore deals 1 damage to each opponent.

Ferocious — At the beginning of each combat, if you control a creature with power 4 or greater, Impressible Cub gets +1/+1 until end of turn.

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.

Death knell — Return an Aura card with mana value 5 or less from your graveyard to the battlefield. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
As long as Inconspicuous Otter is enchanted or equipped, he's a 3/4 legendary Otter Rogue named Agent O and has menace.

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.

Sacrifice Indomitable Bear: Creatures you control gain indestructible until end of turn.

When Inexperienced Martyr dies, each opponent loses 1 life.

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.