msem-instigator

Foretell {B}{R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)
Haste
Whenever Sofia deals combat damage to an opponent, exile the top card of that player's library face down and look at it. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast that spell. Then foretell Sofia. It costs {0} to foretell this way.

When Sofia enters, if it wasn't cast from your hand, it gains lifelink and haste until end of turn.
Whenever Sofia deals combat damage to a player, exile the top card of that player's library face down and look at it. After the current turn has ended, you may cast that spell from exile by paying life equal to its mana value rather than paying its mana cost. If you do, the spell is foretold.
Foretell {B}{R/W} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Lifelink
When you attain Sojourner of the Beyond, create two 1/1 white Spirit creature tokens with flying. They gain haste until end of turn.

First strike

Menace
Whenever a nontoken Warrior you control dies, create a token that's a copy of it, except it's 1/1.

Flying
When Soli's Blessed enters, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Whenever Solvent Tide attacks, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Tap two untapped creatures you control: Harmonize. (Trigger up to one harmony of one permanent you control.)
Harmony — Choose one —
• Soul of New Alores becomes a creature in addition to its other types until end of turn.
• Put two +1/+1 counters on target permanent.

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.

When Soulcarver enters, destroy up to one target non-Demon creature. If you do, create a 2/2 black Demon creature token and draw a card.

First strike, haste
Whenever Soulflare Nymph deals damage to a creature, exile that creature.

Sacrifice a creature: Soulsorrow Shade gets +2/+2 until end of turn.

Flying
When Soulstone Redeemer dies, you may exile target creature. If you do, you gain life equal to its toughness.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
When Sower of Wishes enters, reveal the top three cards of your library. Put all land cards revealed this way into your hand and the rest back on top in any order.

Flying, haste
Whenever Spawn of Hadak attacks, draw a card, then discard a card.

Flying
When Spawn of Keranos enters, you may draw a card. If you do, discard a card unless you control another creature with flying.

Menace
Whenever you cast a cryptic spell, you may return target creature card from your graveyard to your hand. (Artifacts, enchantments and modal spells are cryptic.)

Haste
When Speaker of the Iris enters, abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
Other creatures you control have haste.

Trample
Morph {3}{G}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When you turn Spearhead Ophan face up, creatures you control get +2/+2 and gain trample until end of turn.

When Specimen Collector enters, you may salvage a creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Speckled Outcast has menace as long as it's enchanted.

Flash
Flying
When Spectrum Archmage enters, return target spell to its owner's hand, then abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

Hexproof
Whenever an opponent casts a noncreature spell, put a +1/+1 counter on Spellbane Vulpine.

Flying
{2}, Exile an instant or sorcery card from your graveyard: Spellbone Screecher deals 1 damage to any target.