msem-instigator

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.

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.)

Whenever Merciless Shieldbreaker enters or attacks, target opponent puts three rust counters on a permanent they control with no rust counters on it. That permanent gains “At the beginning of your upkeep, remove a rust counter from this permanent. Then if there are no rust counters on this permanent, sacrifice it and it deals 4 damage to you.”

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.

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

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.

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.

Add three mana of any one color.

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.

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

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.

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.

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.”

Whenever you cast a spell from exile, you may draw a card.
At the beginning of your upkeep, you may reveal the top card of your library.

Double each number and amount of target instant or sorcery spell, activated ability, or triggered ability. Its controller may choose new targets for it. (Amounts are number words, X values, and “a” or “an” used as 1.)

Destroy all creatures without flying.

If a player taps a nonbasic land for mana, that land produces {C} instead of any other type.
Whenever Rylei Wakebreaker attacks, it and another target creature you control each get +1/+0 until end of turn for each attacking creature you control.

Vanishing 3 (This permanent enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a time counter is removed from Burning Heels, exile the top card of your library. Until end of turn, you may play that card.

Gain control of target nonland permanent. The player that controlled it creates a 3/3 blue Squid creature token.

Whenever you cast a noncreature spell, you may pay {U}. If you do or the spell was cast from your graveyard, draw a card.

Flash
When Dehmi, Origin Seeker enters, counter target spell an opponent controls unless that spell's controller has you create X 1/1 red Elemental creature tokens, where X is that spell's mana value.

You may cast target instant or sorcery card from your graveyard this turn. If that spell would be put into your graveyard, exile it instead.

Look at the top eight cards of your library. You may reveal up to one Elf and up to one Dwarf card from among them. Put the revealed cards into your hand and the rest on the bottom of your library in a random order. Tenuous Alliance deals 2 damage to you.

{T}: Add {C}.
{1}, {T}, Sacrifice Perilous Passage: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.

Precursor Sanctum enters tapped. When it does, look at the top three cards of your library, exile one face down, then put the rest on the bottom of your library in any order.
{T}: Add {C}.
{4}, {T}: You may play the exiled card without paying its mana cost. Activate only as a sorcery.