msem-instigator

When Junktrawler enters, create a tapped colorless Powercell artifact token with “{T}: Add {C}.”
Tap another untapped artifact you control: Junktrawler gets +1/+1 until end of turn.

Juvenile Boa gets +2/+0 as long as you control a legendary creature.

Flash
Flying

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
Whenever an instant or sorcery card you own is exiled from anywhere, you gain 1 life.

Creature spells you cast with power 4 or greater cost {1} less to cast.

When Kalak Culler enters, each opponent loses life equal to the number of creatures you've sacrificed this turn.
Revive—{3}{B}, Sacrifice a creature. ({3}{B}, Sacrifice a creature, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Flying, haste
Ward—Pay 3 life.
The first Dragon spell you cast each turn costs {R}{R} less to cast. (This can reduce the amount of generic mana you pay.)

Prowess
You may activate inscribe abilities from your graveyard as though they were in your hand.

Rhapsody {5}{W}{W} (Pay {5}{W}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Kan's Faithful enters, exile up to one target nonland permanent with mana value X or less until Kan's Faithful leaves the battlefield, where X is Kan's Faithful's power.

When Kaneh Scribe enters, amass Soldiers 2. (Put two +1/+1 counters 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.)

Whenever a player discards a card, put a +1/+1 counter on Karatuy.
When a player has no cards in hand, Karatuy becomes a Demon and gains flying and lifelink. This ability triggers only once.
Demoncycling {1}{B}{B} ({1}{B}{B}, Discard this card: Search your library for a Demon card, reveal it, put it into your hand, then shuffle.)

This spell can't be countered.
Trample
Whenever an opponent draws a card except the first one they draw in each of their draw steps, put a +1/+1 counter on Kareki Magehunter.

Vigilance
Revive {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Vigilance
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{2}{W}{W}: Creatures you control get +1/+1 until end of turn.

Whenever Karoa, His Roaring Grace deals combat damage to a player, if he's not equipped, create a colorless Equipment artifact token named Banner attached to him. The token has equip {1} and “Equipped creature gets +1/+1.”

Vigilance, lifelink
{1}, Discard a card: Target Soldier creature gains indestructible until end of turn.

Partner with Shizura, Keeper of Traditions (When this creature enters, target player may put Shizura into their hand from their library, then shuffle.)
Whenever Kasoha, Keeper of Truths or another legendary creature enters, scry 3, then draw a card.

At the beginning of your upkeep, put a +1/+1 counter on Kaur's Gift, then you gain life and add {G} equal to its power. You don't lose that mana as steps, phases, and turns end.
When Kaur's Gift dies, you gain life and add {G} equal to its power. You don't lose that mana as steps, phases, and turns end.

Whenever you cast an instant or sorcery spell, put a +1/+1 counter on Kederekt Seawitch, then scry 1.

When Keen Redtail enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
When Keen Redtail dies, it deals damage equal to its power to any target.

Haste
Whenever Keenheart Blade deals combat damage to a player, you may remove a -1/-1 counter from it.
Persist (When this 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.)

When Keeper of Blue Incense enters, submerge target card from your graveyard. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Flash
When Keeper of Codices enters, you may exile target artifact or enchantment you control. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.

When Keeper of Dark Shadows enters, if it's not a token, target opponent reveals their hand. You may choose a creature card from it. Create a token that's a copy of that card, except it's a colorless Spirit.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
When Keeper of Holy Lands enters, you may search your library for an enchantment card, reveal it, then shuffle and put that card on top of it.