msem-instigator

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

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

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

Scoured Mesa enters the battlefield 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.)

Menace
Sacrifice another artifact: Scrap Buggy becomes an artifact creature until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Scrap, the Second Myr has all activated abilities of other artifact creatures you control.

When Scrapgear Contraption dies, you may put a +1/+1 counter on target creature.

Vigilance, trample

Scrounging Dunes enters the battlefield tapped.
{T}: Add {W} or {B}.
{1}{W}{B}: Until end of turn, Scrounging Dunes becomes a Wurm creature with lifelink in addition to its other types.
Scavenge {1}{W}{B}

When Scrying Pool enters the battlefield, scry 2.
{1}, {T}: Add one mana of any color.

Sculpted Observatory enters the battlefield tapped.
{T}: Add {W} or {U}.
{1}, {T}: Add one mana of any color.

Sea Of Skies Beyond enters the battlefield tapped.
Whenever you cast a noncreature spell, put a creation counter on Sea Of Skies Beyond.
{T}, Remove ten creation counters from Sea Of Skies Beyond and sacrifice it: Shuffle your hand into your library, then draw five cards.

Cards in graveyards lose all abilities.
Cards in graveyards can't be the target of spells or abilities.

When Sealed Riftway enters the battlefield, exile up to one target card from a graveyard.
{2}, {T}, Sacrifice Sealed Riftway: Exile target player's graveyard. Draw a card.

{T}: Add one mana of any color.
{2}, {T}: Draw a card. Activate only if you sacrificed a permanent or discarded a card this turn.

Seaside Citadel enters the battlefield tapped.
{T}: Add {G}, {W}, or {U}.

({T}: Add {U}.)
As Seaside Grotto enters the battlefield, you may pay 1 life. If you don't, Seaside Grotto enters the battlefield tapped.
Basic lands you control have “{T}: Add {U}.”

({T}: Add {G} or {U}.)
Secluded Cascade enters the battlefield tapped unless you control two or more basic lands.

As Secluded Courtyard enters the battlefield, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type or activate an ability of a creature source of the chosen type.

{T}: Add {C}.
{T}, Reappropriate: Add {G} or {W}. (Exile exactly two cards from your hand and/or graveyard.)

When Secluded Monument enters the battlefield, choose a color.
Whenever you cast a spell of the chosen color, Secluded Monument becomes a 5/5 Golem creature until end of turn.

({T}: Add {W} or {U}.)
Whenever Sedate Tundra becomes tapped, you lose 1 life unless you control two or more basic lands.

When Seductive Seashell enters the battlefield, target player mills two cards.
{2}, Sacrifice Seductive Seashell: Target player mills four cards.

({T}: Add {G}.)
Seedshrine enters the battlefield tapped.
When Seedshrine enters the battlefield, you may put a +1/+1 counter on target creature.

{T}, Pay 1 life: Add {B} or {G}.
{1}, {T}, Sacrifice Seedy Bar: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)