msem-instigator

Each creature has haste and “At the beginning of combat on your turn, choose an opponent at random. This creature attacks that player this combat if able.”

At the beginning of combat on your turn, if there are seven or more loyalty counters on Ameret, they become a 5/5 Angel creature with flying and indestructible until end of turn.
[+1]: Create a 1/1 red and white Cleric creature token with lifelink and haste.
[–X]: Ameret deals X damage to any target. You gain X life.

You may activate loyalty abilities of Xirix, the Usurper during extra turns any time you could cast an instant.
[+1]: Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
[–2]: Destroy each nonland, non-Xirix permanent with the greatest mana value among non-Xirix permanents on the battlefield.
[–6]: Put target permanent card from a graveyard onto the battlefield under your control.

Whenever a creature token you control deals combat damage to an opponent, it deals that much damage to each other opponent.
At the beginning of combat on your turn, you may sacrifice another creature. If you do, create a 2/2 red, white, and black Knight creature token with haste.

Noncreature spells you cast cost {1} more to cast.
Noncreature spells your opponents cast cost {1} more to cast unless that player controls more creatures than you.

{T}: Add {C}. Activate only if you have less life and control fewer creatures than each opponent.

Prowess
Curse spells you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Whenever you cast a Curse spell, you may draw a card.

This spell costs {G} less to cast if it targets a blue or black permanent.
Destroy target artifact, enchantment, or planeswalker.

Untap all permanents you control.
Coalesce {5}{G}{U} (You may cast this from your graveyard for {5}{G}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
{G}{U}: Untap Fulfill Twisted Dreams.

Add three mana of any one color.

Poisonous 3 (Whenever this creature deals combat damage to a player, that player gets three poison counters.)
When Soulbreaker of Mautakesh enters, target poisoned player sacrifices a creature.

Oshiruko Whisperwalker can't be blocked except by Rogues.
Whenever a creature is returned to its owner's hand, you may draw a card. If you do, discard a card.

Up to X target creatures gain winnow until end of turn. (Damage dealt to a creature with winnow also causes its controller to lose that much life.)
Rain of Ruin deals 2 damage to each creature.

For each land you control, you may return a land card from your graveyard to the battlefield tapped.

Reverberate—Sacrifice a Swamp. (When you cast this spell, copy it if you paid its reverberate cost.)
All creatures get -2/-2 until end of turn.

Target creature gets +2/+0 until end of turn and can't be blocked except by three or more creatures this turn.
Flashback {U/R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

This spell costs {R} less to cast if it targets a white or blue permanent.
Once Scarred deals 4 damage to target creature or planeswalker.

This spell costs {1}{B} less to cast if it targets a green or white permanent.
Destroy target creature or planeswalker.

This spell costs {1}{U} less to cast if it targets a red or green spell.
Counter target spell.
Draw a card.

This spell costs {W} less to cast if it targets a black or red permanent.
Exile target nonland permanent with mana value 3 or less.

Sacrifice any number of lands. Search your library for that many basic land cards, put them onto the battlefield, then shuffle.

Haste
When Rainy Night Lovers enters, look at the top four cards of your library. You may cast a red instant or sorcery spell with mana value 1 from among them without paying its mana cost. Then put the rest on the bottom of your library in any order.

{T}: Add {C}.
{T}: Add one mana of any color. Activate only if you've cast a noncreature spell this turn.

{T}: Add {C}.
When Krismite Vault is put into a graveyard from the battlefield, create a tapped colorless artifact token named Mox Krismite with “{T}: Add one mana of any color.”

{T}: Add {C}.
{2}: Idravir becomes a 2/2 creature with undying in addition to its other types until end of turn. (When that 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.)