msem-instigator

At the beginning of your end step, for each opponent, destroy up to one target creature that player controls with power less than or equal to the amount of life that player lost this turn.
{3}{R}: Selezzar, Tyrant of Endak deals 2 damage to each opponent.

Enchant creature
When Selfish Epiphany enters, search your library for a card and put that card into your hand. Then shuffle.
Enchanted creature has indestructible and can't be sacrificed.

When Seluriel's Blessing enters, put a +1/+1 counter on each creature you control.
Creatures you control enter with an additional +1/+1 counter on them.
Creatures you control with counters on them have vigilance and indestructible.

[+1]: You gain 1 life. Put a +1/+1 counter on up to one target creature.
[–3]: Exile target creature. Its controller gains life equal to its power.
[–8]: You get an emblem with “Creatures you control get +1/+1 and have double strike and lifelink.”

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.

When Sending Stones enters, harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may trigger a harmony of a permanent card in your graveyard instead.

Death knell — Put a +1/+1, flying, lifelink, or menace counter on Senn, the Haunting Gaze, then trigger a death knell of another permanent you control. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

When Sensational Festivities enters or at the beginning of your upkeep, you may draw a card. If you do, each opponent may draw a card, then discard a card.

Untap all permanents you control during each other player's untap step.

{2/U}, {T}: Target creature gets -4/-0 until end of turn.

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.)

Deathtouch, menace
As long as you control another Knight creature, Ser Joffrey, Plague of Nines and other Knight creatures you control have first strike.

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.

Flying
When Seraph of Renewal leaves the battlefield, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

Flying, vigilance, lifelink
Persist (When this 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.)

Flying
Whenever you cycle Seraph of the Stage or it attacks, audition for white. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Cleric Role giving 2/2 and lifelink. Roles replace older ones.)
Basic landcycling {1}{W} ({1}{W}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

[+1]: Remove all counters from target permanent.
[+1]: Each opponent discards a card.
[–2]: Exile target creature or planeswalker card from your graveyard with mana value less than or equal to the number of lands you control. If you do, create a token that's a copy of it.
[–7]: Each opponent gets an emblem with “At the beginning of your upkeep, you lose 7 life unless you sacrifice seven permanents.”

[+1]: You may sacrifice a permanent. If you do, each opponent sacrifices a permanent that shares a type with it.
[–2]: Put target creature card in a graveyard onto the battlefield under your control.
[–8]: You control target player during their next turn. During that turn, that player may cast spells by paying life equal to their mana value rather than pay their mana cost. After that turn, that player takes an extra turn.

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.

This spell can't be countered.
Flying, protection from cryptic
Whenever you cast a cryptic spell, cast a Sphinx spell, or draw a card, investigate.
{T}, Sacrifice ten Clues: You win the game.

[+1]: Distribute two +1/+1 counters among any number of target creatures you control.
[–1]: Create two 1/1 white Monk creature tokens.
[–6]: Until your next turn, you choose which creatures attack or block and how those creatures attack or block.

[+1]: Create a 1/1 white Warrior creature token with lifelink. You gain 1 life.
[–2]: Put two +1/+1 counters on target creature. It gains double strike until end of turn.
[–7]: Choose up to three creatures, then destroy the rest.

As long as it's your turn, Seto San is a 3/3 Human Warrior creature with indestructible.
[+1]: Up to one target creature you control gains lifelink until end of turn.
[0]: Create a 1/1 white Warrior creature token.
[–X]: Search your library for an Aura or Equipment card with mana value X and put it onto the battlefield, then shuffle.

[+1]: Create two 1/1 white Warrior creature tokens. You gain 2 life.
[–2]: Destroy each creature with the greatest power or tied for the greatest power among creatures on the battlefield.
[–5]: Creatures you control get +X/+X and gain lifelink until end of turn, where X is the number of creatures you control.

Destroy all creatures.