msem-instigator

Whenever a land you control enters, you may tap target creature.

When Shifty Squirrel enters, you gain 3 life.
Sacrifice a creature: Transform Shifty Squirrel.

Menace
Art of war — At the beginning of your end step, if Shikai Hunters dealt damage to an opponent this turn, put a +1/+1 counter on it.

Shikai Revenant enters tapped.
At the beginning of your end step, if an opponent lost life this turn, you may return Shikai Revenant from your graveyard to your hand.

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.

Shining Crusader has protection from all colors as long as you control no colored permanents.

Flash
If one or more counters would be put on a creature you control, put that many plus one of each of those kinds of counters on that creature instead.

Flying
When Shoal Raker enters, draw a card if an opponent is cursed.

Vanguard — Whenever a creature you control attacks alone, Shocking Ewe deals 2 damage to defending player.

When Shokan Captain enters, you may search your library for an Equipment card, reveal it, shuffle, then put that card on top.
Art of war — At the beginning of your end step, if Shokan Captain dealt damage to an opponent this turn, put a +1/+1 counter on it.

Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)
When Shoring Naiad enters, if {U} was spent to cast it, you may return an instant or sorcery card from your graveyard to your hand.

{2/W}{2/W}: Shrapnel Golem deals 3 damage to target creature blocking it.

Haste
Each creature with toughness greater than its power can't block.

Lifelink
Whenever an Aura becomes attached to Shrieking Gnoll, put a +1/+1 counter on Shrieking Gnoll, then target creature an opponent controls gets -1/-1 until end of turn for each +1/+1 counter on Shrieking Gnoll.

Flying
Sacrifice a creature: Shrieking Nightwing gets +1/+1 until end of turn.

Haste
Whenever you sacrifice another permanent, put a +1/+1 counter on Shrine Razer.

Siege Ent can't be blocked by creatures with power 2 or less as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Flash
Whenever you cast Siflir, Elder Pawn or another spell, if you paid an alternate or additional cost to cast it, draw a card.
Wander {3}{U}{U} (You may cast this from the battlefield for its wander cost.)

When Sihari's Groundblazer enters, create a red Aura enchantment token named Searing Crags attached to target land. The token has enchant land, “Enchanted land's name is Charred Causeway” and “Enchanted land has {T}: This land deals 1 damage to each opponent.”

When Silencing Guardian enters, you may have target creature get -1/-1 until end of turn.

Silent Doom enters tapped.
You may cast Silent Doom from your graveyard as long as you sacrificed a permanent this turn.
Cycling {B} ({B}, Discard this card: Draw a card.)

Prevent all combat damage that would be dealt to Silent Reaver.
Prevent all combat damage Silent Reaver would deal to creatures.

Flash
You may cast cryptic spells as though they had flash. (Artifacts, enchantments, and modal spells are cryptic.)

{2}, Pay 2 life: Silkwrap Brawler gains indestructible until end of turn.