msem-instigator

When you cast Senaturian Centurion, reveal cards from the top of your library until you reveal a creature card with mana value 2 or less. Copy that card, then put the revealed card into your hand. You may cast the copy without paying its mana cost. Put the revealed cards on the bottom of your library in a random order.

At the beginning of your draw step, draw an additional card and you lose 1 life. Then if you have six or fewer cards in hand, sacrifice a creature.

When Sentient Contraption enters, create a 1/1 colorless Thopter artifact creature token with flying.

Sentinel of the Highlands has hexproof as long as it's embattled. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Flying, vigilance
Whenever Sepulchral Guide attacks, prevent all combat damage that would be dealt to another target creature you control this turn. If that creature has two or more counters on it, untap it.

Deathtouch
{U/B}: Change a target of target spell or ability that targets Serafina to another creature you control.
Whenever Serafina deals damage to a player, at the beginning of the next end step, that player loses life equal to the life they lost this turn.

Serene Hart can't be blocked by creatures with power 4 or greater.

When Servant of Precursors enters, you gain 4 life and draw a card.

Menace
When Setar Ritualist enters or whenever you cast a spell, if {U}{R} was spent to cast it, Setar Ritualist deals 3 damage to target permanent, then tap that permanent. Put a +1/+1 counter on Setar Ritualist.

Settlement Scout can't be blocked if you control an attacking creature with greater power than it.
Revive {3}{R} ({3}{R}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate this ability only any time you could cast a sorcery.)

At the beginning of your upkeep, you may pay {B}. If you do, return a Wizard card from your graveyard to your hand.

When Sewer Dweller enters or dies, create a 1/1 black Rat creature token with “This creature can't block.”

(Transcend as a sorcery to gain that type and a +1/+1 counter.)
Ward {2}
{2}{U}: Demigod — Exchange a card in your hand and a noncreature, nonland card in your graveyard.
{6}{U}: God — Exchange control of two target permanents that share a card type.

When Sha'Iv Cagemage enters, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an Aura you control enters, you may tap target creature.

When Sha'Iv's Scout enters, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an Aura you control enters, target creature can't block this turn.

Shadowband Consul enters tapped.
{B}, Pay 2 life: Return Shadowband Consul from your graveyard to the battlefield. Activate only if an opponent lost life this turn.

When Shadowstrider dies, create a 2/2 colorless Spirit creature token.

When Shambling Gutless enters, target player discards a card.

When Shapur, the Fifth Shah enters, exile target instant or sorcery card from your graveyard. Until end of turn, you may cast that card. If that spell would be put into a graveyard, exile it instead.
Monument {4}{R} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Return each nonland permanent you don't control to its owner's hand.
Coalesce {6}{U}{U}{U} (You may cast this from your graveyard for {6}{U}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Flying
Glorious end — When Shattered Valkyrie dies, if it was tapped, draw a card for each creature that died this turn.
Sacrifice another creature: Shattered Valkyrie gains indestructible until end of turn.

Trample
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.)
Embattled creatures you control get +2/+0. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

When Shawlbinder enters, if you control a Desert, exile another target permanent. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Revive—{B}, Discard a card. ({B}, Discard a card, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

When Shepherd of Lonely Souls dies, you may return target creature card with mana value 4 or less from your graveyard to your hand.