msem-instigator

Flying
When Skystream Mantas is returned to your hand from the battlefield, draw two cards.

Menagerie — {1}{G}: Slipsand Hornshell gains indestructible until end of turn. Tap it. Activate only if there are five or more creature types among creatures you control.

Sludge-Gill Fox can't be blocked as long as it's attacking alone.
Whenever Sludge-Gill Fox deals combat damage to a player, you may draw a card.

{2}, Remove a +1/+1 counter from a creature you control: Draw a card.

When Smuggler of the Santriza enters, you may discard a card. If you do, draw a card.

({T}: Add {G} or {U}.)
Soaring Rainforest enters tapped.
{1}, {T}: Add {G}{G} or {U}{U}.

({T}: Add {U} or {B}.)
Sodden Cavern enters tapped.

Whenever you cast a noncreature spell, this creature gets +1/+0 and gains first strike until end of turn. Surveil 1.

When Sofia's Swashbucklers enters, you may return target card with foretell from your graveyard to your hand.

Foretell {B}{R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)
Haste
Whenever Sofia deals combat damage to an opponent, exile the top card of that player's library face down and look at it. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast that spell. Then foretell Sofia. It costs {0} to foretell this way.

When Sofia enters, if it wasn't cast from your hand, it gains lifelink and haste until end of turn.
Whenever Sofia deals combat damage to a player, exile the top card of that player's library face down and look at it. After the current turn has ended, you may cast that spell from exile by paying life equal to its mana value rather than paying its mana cost. If you do, the spell is foretold.
Foretell {B}{R/W} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

When Speaker of Open Waters enters, create a green and white Aura enchantment token named Moray's Resolve attached to target creature you control. The token has enchant creature and “Enchanted creatures you control get +2/+2 and have trample and lifelink.”

Creatures your opponents control can't block alone. (They can block different creatures.)

This spell costs {1} less to cast for each other spell you've cast this turn.

Spellwoven Monster can't be the target of spells or abilities in any zone.
As you cast an instant or sorcery spell, reveal cards from the bottom of your library until you reveal an instant or sorcery card. You may add that card's effects to that spell. Then shuffle.

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)

This spell costs {X} less to cast, where X is the number of card types among cards in your graveyard.
Flying, ward {2}

({T}: Add {G}, {W}, or {U}.)
Stalwart Dominion enters tapped.

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

Steel Hunter can't attack unless you control three or more other artifacts.

Cycling {2} ({2}, Discard this card: Draw a card.)

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

When Stillmarsh Brinecatcher enters, return another target nonland permanent to its owner's hand.
At the beginning of your end step, if you control a permanent with mana value 5 or greater, you may sacrifice Stillmarsh Brinecatcher. If you do, draw a card and create a 3/2 colorless Horror creature token.

Stinging Swordfish has first strike as long as it's attacking.
When Stinging Swordfish dies, create an Equipment enchantment artifact token named Fish Sword with “Equipped creature gets +3/+1,” “Equipped creature has first strike as long as it's attacking,” and equip {2}. You may attach that token to a creature you control.

Whenever you cast a spell, if it isn't your main phase, you may have Stoneshrine Guardian's base power and toughness become 4/1 or 1/4 until end of turn.