msem-instigator

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.

At the beginning of your end step, if you lost 2 or more life this turn, create a 1/1 black Bird creature token with flying. If you lost 4 or more life this turn, instead create a 3/3 black Cat creature token with deathtouch. If you lost 6 or more life this turn, instead create a 5/5 black Golem creature token with trample.

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.

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}{W}, {T}: Other creatures you control get +1/+1 until end of turn.

Whenever Inspiring Tactician or another permanent you control becomes the target of a spell or ability you don't control, amass Soldiers 1. (Put a +1/+1 counter on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Inspirited Duelist has double strike as long as it has a +1/+1 counter on it.

Flying
{1}{W}: Exile target artifact you control. Return that card to the battlefield under your control at the beginning of the next end step.

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

Flying
When Intrepid enters, search your library for a land card, reveal it, put it into your hand, then shuffle.
Wanderlust — {0}: Intrepid becomes an artifact creature until end of turn. Activate only if you control four or more differently named lands.

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.)

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Iridescent Familiar enters, if you control another creature with flying, draw a card.

Flying, lifelink
Whenever another creature you control attacks, until end of turn, that creature gets +2/+0 if it's red, +0/+2 if it's green, gains lifelink if it's white, and gains flying it if it's blue.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Spells you cast during combat cost {1} less to cast.

Trample
At the beginning of each combat, you may have Ironhide Bellower deal 3 damage to target creature you control. If you do, Ironhide Bellower gets +3/+0 and can't be blocked by creatures with total power 3 or less until end of turn.

Whenever a creature you control leaves the battlefield, if it had counters on it, you may put one of those counters on Ironpact Marauder.
{1}{B}, Remove two counters from Ironpact Marauder: You draw a card and you lose 1 life.

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

Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)
Whenever Irreguleopard deals combat damage to a player, permutate. (You may remove a counter from a creature you control. If you do, put two +1/+1 counters on a different creature you control.)

Flying
Morph {3}{B}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Ishim of Genesis is turned face up, put a +1/+1 counter on it, then return target instant or sorcery card from your graveyard to your hand.

Flying
Morph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Ishim of the Mists is turned face up, turn all other face-up creature you control face down.

Whenever you cast a noncreature spell, scry 1.
{3}{U}, Exile an instant or sorcery card from your graveyard: Draw a card.

When Isle Conservator enters, if you control a legendary creature, submerge target creature an opponent controls. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Menace
Whenever Issbarren Creeper deals combat damage to a player, draw a card, then discard a card.