msem-instigator

{T}: Add {C}.
{2}, Pay 2 life: Starved Oasis becomes a 4/2 Elemental creature until end of turn. It's still a land.

{T}: Add {C}.
{3}, {T}: Create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Equipped creature gets +1/+0 for each artifact you control.
Equip—Sacrifice an artifact.

Equipped creature has menace.
Sacrifice an artifact or enchantment: Equipped creature gets +2/+2 until end of turn.
Equip {1}

({T}: Add {U} or {R}.)
Steamlit Peaks enters tapped.
{1}, {T}: Add {U}{U} or {R}{R}.

Flying
Whenever a player shuffles their library, Steamquiver Strix deals 2 damage to that player.

When Steamwork Musicians enters, creatures you control get +1/+0 until end of turn.

(Transform this if it's not attached to a creature. Pay {2}{U} as a sorcery to unattach it.)
Enchant creature you control
Steed of the Loch's rider gets +2/+1.
Whenever Steed of the Loch's rider attacks, you may tap target creature an opponent controls.

When Steelscribed Katana enters, you may attach it to target creature you control.
Equipped or inscribed creature gets +2/+1.
Equip {3}
Inscribe {7} ({7}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

({T}: Add {W} or {U}.)
Still Waters enters tapped unless you control two or more basic lands.

{1}, {T}, Sacrifice Stolen Strain: Target creature gains lifelink until end of tun.
{1}, {T}, Sacrifice Stolen Strain: Target creature gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

Stonework Idol's power and toughness are each equal to the number of creatures you control.

At the beginning of your upkeep, if Stonework Infantry is on the battlefield, each player returns all cards named Stonework Infantry from their graveyard to the battlefield.

Whenever you cast an instant or sorcery spell, you may attach Stormbreaker's Edge to target creature you control.
Equipped creature gets +3/+0.
Equip {3}

Whenever equipped creature attacks, it deals damage to defending player equal to the number of instant and sorcery cards in your graveyard.
Equip {2}

Whenever one or more creatures you control attack, you may put a progress counter on Stormcannon Testing.
[PROGRESS 2-3] {T}: Target creature gets +2/+0 until end of turn.
[PROGRESS 4+] {T}: Target creature gets +2/+0 and gains double strike until end of turn.

{T}: Add {C}.
{T}, Exile two cards from your graveyard: Add {U} or {R}.

Stormcharged Pyre enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Other artifacts you control have ward {1}.
Overcast — Whenever you cast an artifact creature spell, if {C} was spent to cast it, it enters with an additional +1/+1 counter on it.

Strange Harbor enters tapped unless you have 15 or less life.
{T}: Add {U} or {R}.

Prowess
Pay 2 life: Change a target of target spell or ability to Straw Intellectual.

Creatures blocking or blocked by Straw Officer have wither. (They deal damage to creatures in the form of -1/-1 counters.)

As Straw Simulacrum enters, choose a creature type.
Straw Simulacrum is the chosen creature type in addition to its other types.
Other creatures you control of the chosen type get +1/+1.

Equipped creature gets +1/+1 and has haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Stunning Cascade enters tapped.
{T}: Add {U} or {R}.
{2}{U}{R}, {T}, Sacrifice Stunning Cascade: Draw a card.