msem-instigator

Enchant player
Creatures enchanted player controls get +0/+1.

{T}: Add {C}.
{2}, {T}: Put target Aura or Equipment card from your graveyard on top of your library.

Storied spells you cast cost {1} less to cast. (Enchantments and legendary cards are storied.)

Haste
Sandstorm Sentinel enters with X +1/+1 counters on it, where X is your fealty to Deserts. (Each Desert you control counts toward your fealty to Deserts.)
Mirage {1}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

When Sandswept Bazaar enters, you gain 2 life.
{T}: Add {C}.

{T}: Add {C}.
{5}, {T}, Sacrifice Sandswept Monument: Create a tapped 4/4 colorless Golem artifact creature token.

Flying, vigilance, lifelink
During each of your turns, you may cast a multicolored spell from your graveyard.

({T}: Add {U}.)
As Saturated Dunes enters, you may pay 1 life. If you don't, Saturated Dunes enters tapped.

Savage Lands enters tapped.
{T}: Add {B}, {R}, or {G}.

({T}: Add {G}.)
Savage Sanctuary enters tapped with two sanctum counters on it.
{T}, Remove a sanctum counter from Savage Sanctuary: Add {R} or {W}.

Creature spells you cast cost {2} less to cast.
Whenever a creature you control enters, if it doesn't have vanishing, put four time counters on it and it gains vanishing.

When Scabrous Automaton dies, draw a card, then add {C}{C}. Until end of turn, you don't lose this mana as steps and phases end.

(Transform this if it's not attached to a creature. Pay {1}{R} as a sorcery to unattach it.)
Enchant creature you control
Scale Bearer's rider gets +4/+3 and has flying and haste.
Whenever Scale Bearer's rider attacks, you may pay {2}{R}. If you do, it deals damage equal to its power to target creature or planeswalker.

Whenever Scaleblight Cutthroat attacks, each opponent loses life equal to its power.
{4}{B}{B}: Scaleblight Cutthroat gets +3/+3 until end of turn.

Equipped creature gets +1/+1.
Equipped creature has “When this creature dies, if it's not a token, create a token that's a copy of it except it's a colorless Spirit Dragon with flying in addition to its other abilities.”
Equip {2}

When Scanning Module enters, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
Equipped creature gets +1/+1.
Equip {1}

Enchant player
Whenever enchanted player taps a nonbasic land they control, that land doesn't untap during its controller's next untap step.

Scavenger Holdout enters tapped.
When Scavenger Holdout enters, you may pay {3}. If you do, create two 1/1 green Scout creature tokens.
{T}: Add {C}.

{3}, {T}: Draw a card.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)
Whenever Scavengermobile deals combat damage to a player, choose land or nonland, then rediscover a card of that kind. (Look at the top card of your library. You may reveal it and put it into your hand if it's a card of the chosen type. Otherwise, put it back or into your graveyard.)

When Scintillating Tome enters, choose a nonbasic card name.
{T}: Scry 1, then you may reveal the top card of your library. If a card with the chosen name is revealed this way, put it into your hand.

As Scorched Copse enters, you may tap an untapped creature you control. If you don't, Scorched Copse enters tapped.
{T}: Add {R} or {G}.

Equipped creature gets +2/+2.
{1}: Attach Scoundrel's Aetherlock to target Rogue.
Equip {2}

Scoured Barrens enters tapped.
When Scoured Barrens enters, you gain 1 life.
{T}: Add {W} or {B}.

Scoured Mesa enters tapped.
{T}: Add {W}.
Desertcycling {1}{W} ({1}{W}, Discard this card: Search your library for a Desert card, reveal it, and put it into your hand, then shuffle.)