msem-instigator

Whenever you cast an instant or sorcery spell, target creature can't block this turn.

Resolute — {T}: Grizzled Cutthroat deals 1 damage to any target. Activate only if Grizzled Cutthroat's power is greater than its base power.

{2}, Sacrifice a creature or artifact: Hadak's Guardian deals 2 damage to any target.

When Hand of Fury enters, it gets +2/+2 and gains haste until end of turn.
At the beginning of your upkeep, if your fealty to Mountains is five or greater, transform Hand of Fury. (Each Mountain you control counts towards your fealty to Mountains.)

When Hate-Driven Arsonist enters, you may have it deal X damage to target creature or planeswalker, where X is the number of instant and sorcery cards in your graveyard.

Haste (This creature can attack and {T} as soon as it comes under your control.)
Mirage {R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Elemental, instant, and sorcery spells you cast cost {1} less to cast.

Haste
Whenever Herald of the Humble deals combat damage to a player, that player reveals the top card of their library. If it's a nonland card with mana value 3 or less, they may cast it without paying its mana cost.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, scry 1.

Whenever an opponent casts a spell during your turn, Hunter of Incantations deals 2 damage to that player.

{R}, Tap two untapped artifacts you control: Incineration Expert deals 1 damage to any target.
{3}{R}, Tap eight untapped artifacts you control: Incineration Expert deals 8 damage to any target.

Whenever you cast an instant or sorcery spell, Infernal Immolator deals 2 damage to each opponent.

At the beginning of combat on your turn, create a 1/1 blue and red Pirate creature token with haste. That token attacks this combat if able.
Whenever Intrepid Captain attacks, other attacking Pirates you control get +1/+0 until end of turn.

Flying, haste
Dominance — At the beginning of combat on your turn, if you control the creature with the greatest power or tied for the greatest power, you may pay {1}{R}. If you do, return Issbarren Phoenix from your graveyard to the battlefield.

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.

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.

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.)

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.)

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.

Whenever you cast a spell during another player's turn, monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)

Whenever Lone Freelancer becomes blocked, it deals damage equal to its power to defending player.

Haste
When Maddened Inferno leaves the battlefield, discard a card, then draw two cards.
Evoke {1}{R} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Haste
Whenever Malformed Mongrel deals combat damage to a player, discard a card.

Whenever a nonbasic nontoken land enters under an opponent's control, create a tapped colorless land token named Fading Rift with “{T}, Sacrifice this land: Add one mana of any color.”

Whenever an artifact you control enters, Master of Munitions deals 1 damage to each opponent.