msem-instigator

First strike
Whenever Keeper of the Banner deals combat damage to a player, draw two cards, then discard two cards.

{T}: Keepers of the Reach deals 1 damage to each opponent.
{2}{R}, {T}: Keepers of the Reach deals 3 damage to each opponent. Activate only if you control a permanent with mana value 5 or greater.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{2}{R}, {T}: Target creature can't block this turn.

Kernel Barrage deals damage to target creature or planeswalker equal to the number of spells you've cast this turn (including this one).
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Enchant opponent
Creatures attacking enchanted player get +2/+0.
{R}, Discard Kernel Flare: Draw a card.

Whenever Kessig Jeweler attacks, you may discard a card. If you do, draw a card.
{1}{R}: Transform Kessig Jeweler. Activate only if it's attacking.

At the beginning of your first main phase, you may discard a card. If you do, draw a card and create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
At the beginning of your end step, if Kessig Tombrobber didn't attack this turn, transform it.

Cast Khalizors' Last Stand only during your postcombat main phase.
Gain control of target creature until end of turn. Untap all creatures you control. They gain haste until end of turn. After this phase, there is an additional combat phase followed by an additional main phase.

Choose one —
• Kilnfire deals 1 damage to each creature and planeswalker target player controls.
• Destroy target artifact.

Add two mana in any combination of colors. (Then exile this card. You may cast the creature later from exile.)

Improve {R/W} ({R/W}: 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 an embattled creature you control attacks, you may exile the top card of your library. During any turn you attacked with an embattled creature, you may play that card. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Kinjiru Assailant has haste as long as an opponent controls a nonbasic land.

When Kinken, the Dragon's Breath enters, draw a card, then choose a creature card name.
Whenever a creature you control with the chosen name attacks, you may pay {1}. If you do, create a token that's a copy of it and that's tapped and attacking, except it isn't legendary. Exile the token at the beginning of the end step.

Whenever you cast a spell that targets one or more permanents you don't control, gain control of those permanents until end of turn. Untap them. They gain haste until end of turn.

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Whenever Knight of the Cockatrice attacks, you may pay {1}{R}. When you do, target creature can't block this turn.

Whenever Knight of the Hawk deals combat damage to a player, you may sacrifice it. If you do, search your library for a red legendary creature card, reveal it, put it into your hand, then shuffle.

This spell costs {1} less to cast for each embattled creature you control. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)
Haste
Whenever Knights of the Burning Pyre attacks, it deals X damage to each opponent, where X is the number of embattled creatures you control.

Target creature gets +2/+1 until end of turn. If it's a Pirate or Rogue, it gains first strike until end of turn.

Reach
Knotweald Ranger can't block creatures without flying.

Creatures you control get +1/+0 for each color among permanents you control and have haste.
Whenever you cast a white, blue, black, or green instant or sorcery spell, copy it for each of its colors. You may choose new targets for the copies.

Koth's Retaliation deals 4 damage to target creature. When that creature dies this turn, exile its controller's graveyard.

[+1]: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.
[–2]: Koth, One True Hero deals damage to target creature equal to the number of Mountains you control.
[–7]: Create X 3/1 red Elemental creature tokens with trample and haste, where X is the number of Mountains you control.

Destroy target land. Create a 1/1 red Goblin creature token.

First strike, haste
Whenever Kragnoss' Battlecharger attacks, it gets +1/+0 until end of turn for each attacking creature.

Haste
When Kragnoss, Rebellion Commander enters, create a 1/1 red Goblin creature token.
Whenever a Goblin you control attacks, Kragnoss, Rebellion Commander deals 1 damage to target creature defending player controls.