msem-instigator

Haste (This creature can attack and {T} as soon as it comes under your control.)

Eureka! (At the beginning of each end step, you get a research counter if you cast a spell this turn. Then if you have eight or more research counters, remove them and create a Masterpiece token of your choice.)
Whenever you cast a noncreature spell, create a 1/1 colorless Construct artifact creature token.

Deathtouch
As long as there are five or more different creature types among creatures you control, Itinerant Stalker gets +1/+0 and must be blocked if able.

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.)

Art of war — At the beginning of your end step, if Jaakuna Betrayer dealt damage to an opponent this turn, you may discard a card. If you do, draw a card.

Double strike
Art of war — At the beginning of your end step, if Jaakuna Tyrant dealt damage to an opponent this turn, put a +1/+1 counter on it.

Vigilance
Augmented — Whenever Jacque attacks, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, you may exile any number of target nonland permanents, then return them to the battlefield tapped under their owners' control.

Artifact creatures you control get +1/+1.
{U}{R}, Sacrifice an artifact: Create a 1/1 colorless Servo artifact creature token.

Activated abilities you activate cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.
Attain {5}{U} ({5}{U}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Jara Favored gets +2/+2 as long as you've lost life this turn.

Trample, haste
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.)

Menace
Inspired — Whenever Jeering Kit becomes untapped, target Fox you control gets +1/+1 until end of turn.

Vigilance
{1}{W}: Jhessian Cavalier gains lifelink until end of turn.

You may look at the top card of your library any time.
Once during each of your turns, you may play a land from the top of your library as though you could play an additional land.
{3}{G}{G}: You may cast the top card of your library without paying its mana cost if it's a creature card. Activate only as a sorcery.

Whenever one or more creatures deal combat damage to you, put a -1/-1 counter on one of them.
Attain {5}{W} ({5}{W}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

When Jobiah, Devoted Farmer enters, search your library for a land card, put it onto the battlefield tapped, then shuffle.
At the beginning of your upkeep, if you control six or more lands with different names, you may transform Jobiah.

Johanna, Skarvith Marshal has first strike as long as it's attacking.
Whenever you attack, you may pay {X}{R/W}{R/W}. When you do, put a +1/+1 counter on each of up to X target attacking creatures. Those creatures gain first strike until end of turn.

If another creature you control would die, exile it instead.
When John Furo, the Unfortunate dies, until your next end step, you may play cards exiled with John Furo.

Menace, lifelink
Whenever Jonah of the Spellbane deals combat damage to a player, destroy target creature or planeswalker, then scry 1.

Whenever Journeying Giftbearer or another nontoken creature you control enters, create a green and white Aura enchantment token named Wild Boon attached to that creature. The token has enchant creature and “Enchanted creature gets +1/+1.”

When Joyful Deviant enters or dies, it deals 1 damage to any target.

As Joyous Chromatelk enters, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.
{T}: Add one mana of the chosen color.

Trample
Whenever this creature attacks, if you control three or more other creatures, it gets +2/+1 until end of turn.

Menace
Swampcycling {1}, forestcycling {1} ({1}, Discard this card: Search your libary for a Swamp or Forest card, reveal it, put it into your hand, then shuffle.)