msem-instigator

{1}, Sacrifice a creature: Each opponent loses 1 life and you gain 1 life.

All creatures get -2/-2 until end of turn. At the beginning of the next end step, if three or more creatures died this turn, create two tapped Treasure tokens.

Whenever you cast a noncreature spell, torment each opponent. (They lose 3 life unless they discard a card or sacrifice a nonland permanent.)
{3}{U/B}{U/B}: Draw a card for each opponent with ten or more cards in their graveyard. You lose that much life.

Flying
Once each turn, when a creature an opponent controls dies, you may create a Treasure token.
{3}{B/R}{B/R}: Search target opponent's library for a card and exile it face down. Then that player shuffles. You may look at and play that card for as long as it remains exiled. Activate only once each turn and only as a sorcery.

Menace, haste
As long as Arleigh, Spellblade Prodigy is tapped, the first spell you cast during each other player's turn costs {U/R} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a spell with mana cost {1}{R}, it costs {1} to cast.)

Prowess
Whenever Balefire Conjurer attacks, you may pay {1}{R}. If you do, exile the top card of your library. You may play that card until the end of your next turn.

Improve {1}{R} ({1}{R}: 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.)
As long as Bloodbelly Glutton is embattled, it has first strike, menace, and haste. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Burning Grasp deals 3 damage divided as you choose among one or two targets.
Draw a card.

Cleave deals 1 damage to each opponent and 1 damage to each creature and planeswalker your opponents control.

Haste
{T}: Dragonfire Sniper deals 1 damage to target creature or planeswalker and 1 damage to that permanent's controller.

When Dragonheart Seer dies, you may exile it. If you do, return up to two target instant and/or sorcery cards from your graveyard to your hand.

As an additional cost to cast this spell, discard a card.
Draw two cards and create a Treasure token.

When Dwarven Tunnelers enters, create a tapped Treasure token.
{T}: Target creature with power 2 or less can't be blocked this turn.

Haste, prowess
{3}{R}, {T}, Sacrifice Emberheart Arcanist: Return target instant or sorcery card from your graveyard to your hand.

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Fiery Explosion deals 5 damage to target creature or planeswalker.

Each player discards their hand. Draw up to two hands of seven cards. Shuffle all but one of your hands into your library. Each other player draws seven cards.

{7}{R}: Up to three target creatures you control get +3/+0 and gain menace until end of turn. This ability costs {2} less to activate if you control a legendary creature.

Improve {R} ({R}: 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 Galdurheim Reaver attacks, it deals damage to the player or planeswalker it's attacking equal to the number of embattled creatures you control. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Once each turn, when you cast a creature spell, you may copy it for each other spell you cast this turn. (A copy of a creature spell becomes a token.)
Whenever Garragrok, Horde Tyrant attacks, add {R}{R}{G}{G}. Until end of turn, you don't lose this mana as steps and phases end.

Trample
Whenever Hellfire Titan enters or attacks, exile the top card of your library and up to one target instant or sorcery card with mana value 3 or less from your graveyard. Until the end of your next turn, you may play those cards.

Flying
If a source would deal damage to an opponent, it deals double that damage to that player instead.

Enchant creature
You may cast this spell from your graveyard if it targets a legendary creature you control.
Enchanted creature gets +2/+2 and has haste.

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

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

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.