msem-instigator

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.

As long as Inconspicuous Platypus is enchanted or equipped, he's a 3/3 legendary Platypus Rogue named Agent P and can't be blocked.

Whenever you cast a noncreature spell, upgrade Indecisive Sorceress. When you can't, remove all counters from it and it deals damage to any target equal to the number of counters removed this way.
• +1/+1
• Flying
• First strike

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

Whenever you cast an instant or sorcery spell, Infernal Immolator deals 2 damage to each opponent.

Haste
When Inferno Forerunner enters, you may have target creature gain haste until end of turn.

Hexproof
Whenever another creature you control becomes the target of a spell an opponent controls, you may submerge that creature. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)
{1}{U}{U}: Turn target face-down creature you control face up.

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

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

When Ingredient Scroungers enters, if you control a creature with deathtouch, return target permanent card from your graveyard to your hand.

Flying
Attain {4}{B} ({4}{B}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Whenever Inishtu, Desert Healer enters or attacks, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
At the beginning of your upkeep, if seven or more cards are in your graveyard, you may transform Inishtu.

{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.

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

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

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

Flying
When Inspirational Beacon enters, you gain 3 life.

When Inspired Blade enters, if you control another Warrior, draw a card.

When Insurgent Racketeer enters or dies, you may discard a card. If you do, draw a card.

Interan Soothsayer gets +1/+1 for each other green creature you control.
{G}, {T}: Put a +1/+1 counter on target green creature.

At the beginning of combat on your turn, create a 1/1 blue and red Pirate creature token with haste. That token attacks this combat if able.
Whenever Intrepid Captain attacks, other attacking Pirates you control get +1/+0 until end of turn.

Improve {W} ({W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever one or more embattled creatures you control attack, create a 1/1 white Cleric creature token with lifelink. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Flash
When Intrepid Shooter enters, it deals 2 damage to target attacking creature.

Flying, trample, lifelink

First strike
Whenever you cast an artifact or enchantment spell, put a +1/+1 counter on Ironclad Infantry.