msem-instigator

Whenever you cast a spell, you may cast a spell from your hand with lesser mana value without paying its mana cost.
You can't cast more than one spell of each card type each turn.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When Idleglen Instructor enters, draw a card, then discard a card.

Flying
Whenever Idol of the Dead God deals combat damage to a player, search your library for any number of creature cards named Idol of the Dead God, reveal them, put them into your hand, then shuffle.

{T}: Add {C}.
{2}: Idravir becomes a 2/2 creature with undying in addition to its other types until end of turn. (When that creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Each nontoken land you control has all activated abilities of each other land on the battlefield.
When Idyll leaves the battlefield, until the end of your next turn, you gain “Each nontoken land you control has all activated abilities of each other land on the battlefield.”

Idyllic Oasis enters tapped unless you control a Plains.
{T}: Add {G} or {U}.

Concord — At the beginning of your upkeep, if there are four or more card types among permanents you control, you gain 1 life and create a 1/1 blue Jellyfish enchantment creature token with slipstream. (It can't be blocked as long as only creatures with slipstream are attacking.)

Flying, vigilance, lifelink
Idyllic Pegasus gets +1/+0 for each artifact and/or enchantment you control.

Search your library for an enchantment card, reveal it, put it into your hand, then shuffle.

When Iekin's Portal enters, look at the top five cards of your library. Put one into your hand and the rest into your graveyard.
{1}{U}{U}: Transform Iekin's Portal. Activate only if your fealty to Islands is five or greater.

Augmented — When you cast If Memory Serves, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, copy it twice. You may choose new targets for the copies.
Return target permanent card with mana value 3 or less from your graveyard to the battlefield. Exile If Memory Serves.

Ifram's Cavalier enters with two additional +1/+1 counters on it if you didn't cast it from your hand.

Haste
Ifram's Emissary gets +1/+1 as long as you control a green or blue permanent.

Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)
Ifram's Greenfur must be blocked each combat if able.

{G}{U}{R}, Discard a card named Ifram, God of Chaos: Ifram gains indestructible and becomes a God creature in addition to its other types.
Whenever Ifram enters or attacks, choose target non-God permanent. Its owner shuffles it into their library, then its controller reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Igneous Pulverizer desecrates a permanent, destroy target nonland permanent.

Ward—Pay 3 life.
Igniderm enters with three ignition counters on it.
At the beginning of your upkeep, remove an ignition counter from Igniderm. If you can't, sacrifice it.

Vigilance
Once each turn, when you cast an instant, sorcery, or Elemental spell, you may put a +1/+1 counter on Ignited Vanguard.

At the beginning of combat on your turn, gain control of another target permanent until end of turn. Untap that permanent. It gains haste until end of turn.
Fleeting {2}{R}{R} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

{R}: Igniting Lavaling gets +1/+0 until end of turn.
{4}{R}, Sacrifice Igniting Lavaling: It deals 3 damage to any target.

Once each turn, when you gain life, you may exile the top card of your library. You may play that card this turn.
Whenever you cast your second spell each turn, Ignition Engine deals 2 damage to target player or planeswalker.

Ignition Point deals 3 damage to any target.
The next card you cast this turn can be cast as though it has flash.

As an additional cost to cast this spell, pay X life.
Ignition Ritual deals X damage to each creature and each planeswalker.

You get a fuse counter, then Ignition Sequence deals X damage to any target, where X is 2 plus the number of fuse counters you have.

When Ikari-no-Oni enters, other creatures you control get +1/+0 until end of turn.