msem-instigator

First strike
Whenever an opponent casts a spell, Kiboshi's Guardian gains indestructible until end of turn.

When Kin of the Rainforest enters, you may put a land card from your hand onto the battlefield.
Ascend {1}{R} ({1}{R}: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

When Kiri Yoroi enters, create a 2/2 colorless Spirit creature token and attach Kiri Yoroi to it.
Equipped creatures you control get +1/+1.
Equip {2}

When Kizoku Valiant enters or dies, you gain 2 life.
Art of war — At the beginning of your end step, if Kizoku Valiant dealt damage to an opponent this turn, put a +1/+1 counter on it.

When Kofe-District Scholar enters, draw a card. If Kofe-District Scholar's paranoia cost was paid, draw two cards instead.
Paranoia {1}{U}{U} (You may cast this spell for its paranoia cost when a permanent you control leaves the battlefield.)

At the beginning of your end step, if an opponent lost life this turn, Kogane the Crimson Consort deals 2 damage to each opponent and you gain 2 life.

Creatures you control have protection from legendary. (Those creatures can't be blocked, targeted, dealt damage, or enchanted by anything legendary.)

Konoe's Lieutenant gets +1/+1 as long as an opponent controls a legendary permanent.

Art of war — At the beginning of your end step, if Kowareta Informant dealt damage to an opponent this turn, draw a card, then discard a card.

Sacrifice Kumo-no-Oni: Prevent all combat damage that would be dealt this turn.

Art of war — At the beginning of your end step, if Kurayami Butcher dealt damage to an opponent, you may destroy target creature that was dealt damage this turn.

Whenever another nontoken creature you control dies, you may exile it. If you do, create a 2/2 colorless Spirit creature token.

{T}: Add {C}.
Tap an untapped creature you control: Kurayami Shrine becomes a 1/1 Spirit creature with deathtouch until end of turn. It's still a land.

Art of war — At the beginning of your end step, if Kuryu Swordsman dealt damage to an opponent this turn, you may have Kuryu Swordsman fight target creature you don't control. (Each deals damage equal to its power to the other.)

Whenever an opponent casts a noncreature spell, put a +1/+1 counter on target creature you control.

At the beginning of each opponent's draw step, that player draws an additional card, then discards a card.
Whenever an opponent discards a card, you draw a card and you gain 1 life.

Trample
Other creatures you control get +1/+1 and have trample.

Until end of turn, creatures you control get +1/+1 and gain trample and poisonous 1. (Whenever one of those creatures deals combat damage to a player, that player gets a poison counter.)

As an additional cost to cast this spell, sacrifice a creature.
Target creature gains +4/+4 until end of turn.

Exile target artifact or enchantment. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Enchant creature
Enchanted creature and all other creatures with the same name as that creature can't attack or block.

Whenever Leyline Tracer attacks, exile the top card of your library. Until end of turn, you may play that card.
Ascend—{B}, Discard two cards. ({B}, Discard two cards: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

Library Specter can't attack unless there are five or more noncreature, nonland cards in your graveyard.

When Life's Harbinger dies, you may put a +1/+1 counter on target creature you control.
{T}: Add {G}.

Enchant creature
Enchanted creature gains +X/+X, where X is your life total.
When enchanted creature dies, shuffle Life's Will into its owner's library.