msem-instigator

Each creature with a law counter on it can't attack or block.
{2}{W}, {T}: Remove all law counters from all permanents, then put a law counter on target creature.

Whenever Supreme Mechanothurge or another artifact you control enters, up to one target artifact you control becomes a copy of another target artifact or creature you control, except it's an artifact in addition to its other types.

When Suraj Militant enters, target creature gets +1/+1 until end of turn.

{2/R}: Suraj Outrider gets +1/+0 until end of turn.

Target creature gets +3/+0 and gains first strike until end of turn.

Identity — Sureshot Recruit has reach as long as you control at least two other creatures that share a creature type with it.

Haste
Ward—Pay 3 life.
Whenever Surface Expeditioneer attacks, if it's embattled, it deals 2 damage to target player or planeswalker. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Target creature gets +2/+2 and gains trample until end of turn.
Reprise {2}{R} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

Target creature gets +X/+X until end of turn.
Fabled {X}{R}{R} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that creature.)

As Surge of the Fellors enters, choose Fellor or Lafterii.
• Fellor — Warriors you control have haste.
• Lafterii — Wizard creatures you control have “{2}{R}, {T}: This creature deals 1 damage to target player or planeswalker.”

Search your library for a basic land card and put it onto the battlefield, then shuffle.
Orchestrate {1}{G} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

Enchant creature
Enchanted creature has haste and first strike.

Surging Lightning deals 2 damage to target creature or planeswalker. If you've cast another spell this turn, it deals 4 damage instead.

Submerge up to two target attacking nontoken creatures an opponent controls. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

You may have Surging Wurm assign its combat damage as though it weren't blocked.
Surging Wurm gets +2/+2 as long as seven or more cards are in your graveyard.

Target player draws X cards.

Target creature gains double strike and trample until end of turn. (Then exile this card. You may cast the creature later from exile.)

Until end of turn, target creature gets +1/+1 and gains lifelink.

Flash
When Surreal Bakhtak enters, choose one —
• Destroy target tapped creature.
• Tap up to three target creatures.

Flying, prowess
Whenever Surveyor of Skies attacks, you may return a permanent you control to its owner's hand.

When Surveyor's Rifle enters, rediscover a land card. (Look at the top card of your library. You may reveal it and put it into your hand if it's a land card. Otherwise, put it back or into your graveyard.)
Equipped creature gets +2/+1.
Equip {3}

Wanderlust — When you cast this spell, you may copy it if you control four or more differently named lands. You may choose new targets for the copy.
Untap target creature you control. It gets +1/+1 and gains hexproof and indestructible until end of turn.

Regenerate target creature. (The next time this would be destroyed this turn, it isn't. Instead tap it.)

Return up to one target creature card and up to one target land card from your graveyard to your hand.

Spells you cast have trial 2. (As you cast them, an opponent of your choice may pay 2 life. If they don't, they fail the trial.)
Whenever an opponent fails a trial of a creature spell, that creature enters with an additional +1/+1 counter on it.
Whenever an opponent fails a trial of a noncreature spell, create a tapped Treasure token.