msem-instigator

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.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 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.)

Enchant land
Enchanted land has “{T}: Draw a card, then discard a card.”

When Irrigation Trawler enters, reveal the top card of your library. If that card was a land card, put that card into your hand. Otherwise, create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”

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.

Whenever a creature you control dies, each opponent loses 1 life and you gain 1 life.
{2}{W}{B}: Ishim's Meddling becomes a 4/4 Angel creature with flying and vigilance until end of turn.

Enchant permanent
Enchanted permanent loses all abilities except for mana abilities and has no name.

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

Flash
When Issbarren Warden enters, exile target token.

Menace (This creature can't be blocked except by two or more creatures.)
Itava Warshrieker attacks each combat if able.

Artifact creatures you control get +1/+1.
{1}{U}, Discard an artifact card: Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Whenever you cast a creature or planeswalker spell, if mana produced by a nonland permanent was spent to cast it, it gains trample and haste until end of turn.
{T}: Add {R} or {G}.

Paranoia—Reappropriate white. (You may cast this spell by exiling two white cards from your hand and/or graveyard when a permanent you control leaves the battlefield.)
When Ivenge's Evangel enters, create a 1/1 white Cleric creature token and you gain 1 life.

If an enchanted permanent you control would leave the battlefield, instead destroy one of the Auras attached to it, then that permanent phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Whenever Ivory Curtain Producer attacks, if it's enchanted or you cast a spell that targeted it this turn, create a 1/1 colorless Construct Actor creature token.

Improve {1} ({1}: 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 Ivy Kissinger, Sharpshooter attacks, choose a creature you control. For each kind of counter among creatures you control, you may put a counter of that kind on the chosen creature.

Vigilance
{3}{W}, {T}: Tap target creature. This ability costs {3} less to activate as long as J-7 Freeze Frame is a creature.
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)

When Jade Counterweight enters, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Equipped creature gets +1/+1.
Equip {1}

All lands gain “{T}: Add one mana of any color” and lose all other abilities.

Equipped creature gets +2/+1.
Equip {2}

Whenever Jak, Daring Vanguard or another legendary creature you control enters, creatures you control get +1/+0 and gain haste until end of turn.

You gain 5 life. Then draw a card if you've lost life this turn.