msem-instigator

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.

When Seven Deadly Sins has seven or more sin counters on it, sacrifice it.
{B}{B}, Put a sin counter on Seven Deadly Sins: Destroy target creature. This ability costs {1} more to activate for each sin counter on Seven Deadly Sins.

Destroy target creature or planeswalker. If you controlled a black legendary creature or planeswalker as you cast this spell, that permanent's controller loses X life and you gain X life, where X is that permanent's mana value.

[+1]: Create a 1/1 green Scout creature token. If you control six or more lands, also create a 1/1 white Bird creature token with flying.
[–1]: Reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put it into your hand.
[–5]: You get an emblem with “Whenever each permanent you control becomes tapped for the first time each turn, untap it.”

Flying
When Sha Long enters, each player chooses an artifact they control, then sacrifices the rest. If they don't control an artifact, they may return an artifact card from their graveyard to the battlefield. Repeat this process for creatures, enchantments, and planeswalkers.

{U}{R}{W}, Discard a card named Sha'Iv, God of Order: Sha'Iv gains indestructible and becomes a God creature in addition to its other types.
Whenever Sha'Iv enters or attacks, choose target creature an opponent controls. Untap it, then tap each other creature that player controls. They don't untap during their controller's next untap step.

Whenever a nontoken Satrapy you control enters, create a token that's a copy of it, except it's a 1/1 blue Spirit creature in addition to its other types.
Tap seven untapped Satrapies you control: Exile cards from the top of your library until you exile a nonland card. You may cast that card without paying its mana cost.

When Shala Na enters, each player chooses a creature they control, then sacrifices the rest.
[+1]: Up to one target creature you control gains double strike and haste until end of turn.
[–6]: You get an emblem with “Whenever a creature dies, each opponent loses 2 life.”

[+1]: Up to two target creatures you control each get +1/+0 and gain first strike until end of turn.
[0]: You may sacrifice a creature. If you do, Shala Na, Urshadi Apostate deals 3 damage to any target.
[–3]: Discard your hand, then draw three cards.

Choose two —
• Each opponent sacrifices a creature with mana value 3 or less.
• Each opponent sacrifices an enchantment with mana value 3 or less.
• Exile each opponent's graveyard.
• You gain 3 life.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Whenever a creature enters, its controller sacrifices another creature other than Shan Jun.
{W}{B}: Demigod — Exile each opponent's graveyard. Shan Jun gains protection from each name among cards exiled this way.
{6}{W}{B}: God — Target opponent creates a 1/1 white Avatar creature token with “When this creature dies, you lose the game.”

When Shara, Prime Geneticist enters, if X isn't 0, create two X/X green Mutant creature tokens.
[+1]: Surveil 2. At the beginning of your next end step, untap up to one permanent.
[–2]: Conjure a card named Test Run into your hand. (It's a sorcery that costs {X}{G} with “Create an X/X green Mutant creature token. Draw a card.”)
[–7]: Search your library for a card and put it into your hand. Repeat this process once for each token you control. Then shuffle.

Return up to two target cards from your graveyard to your hand. Put Shared Reminiscence on the bottom of its owner's library.

Each creature you control has base power and toughness X/Y, where X is the greatest base power among creatures you control and Y the greatest base toughness among creatures you control.

Flash
Flying
When Sharuum, Archmagocrat enters, return to the battlefield all nonlegendary artifact cards in your graveyard that were put there from the battlefield this turn.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Ward—Discard a card.
{B}{R}: Demigod — Draw a card, then discard a card. You may have each opponent sacrifice a nonland permanent with the same mana value as the discarded card.
{4}{B}{R}: God — Create two tokens that are copies of Shi Hou's back face.

Trample
When Shigurei, the Floodbringer enters, up to three target permanents become colorless Island lands.

Flying, haste
Whenever Shimmering Dragon attacks, for each creature you control, create a tapped and attacking token that's a copy of that creature. Exile the tokens at the beginning of the end step.

Whenever equipped creature attacks, put a charge counter on Shimmersting, then create a token that's a copy of equipped creature and that's tapped and attacking for each charge counter on Shimmersting, except the tokens aren't legendary. Exile the tokens at the beginning of the end step.
Equip {5}

Whenever Shina Taiyohata or another creature you control enters, you may have that creature gain haste. If you do, return that creature from the battlefield to its owner's hand at the beginning of the next end step.

[+2]: Exile any number of target artifacts and/or enchantments you control, then return them to the battlefield under your control. You may draw that many cards.
[–4]: Search your library for an enchantment card, put that card onto the battlefield, then shuffle.
[–12]: Put any number of permanent cards you own from outside the game onto the battlefield tapped.

Flying, lifelink
Whenever Shioki, Imperial Heir attacks, exile any number of other target nonland permanents you control, then return those cards to the battlefield under their owner's control.

Equipped creature gets +2/+2 and has flying and lifelink.
When equipped creature deals combat damage to a player, unattach Shionoshio, Ocean's Vow, then transform it.
Equip {W}{U}
Shionoshio can be your commander.