msem-instigator

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

{2}{B}, {T}, Sacrifice Sculler's Oar: Return up to two target creature cards from your graveyard to your hand.

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

Enchant creature
Enchanted creature gets +2/+2.
Enchanted creature has hexproof as long as it's tapped.

When Scuripi Collector enters, return target artifact, enchantment, or land card from your graveyard to your hand.

Vigilance
{T}: Add {G}.

Whenever you sacrifice a permanent, you may pay {1}. If you do, you draw a card and you gain 1 life.

Until end of turn, target creature gains “When this creature is dealt damage, destroy it.” (Then exile this card. You may cast the creature later from exile.)

{2}{R}: Target creature can't block this turn.

At the beginning of your upkeep, if six or more cards are in your graveyard, you may transform Scuttling Gnat.

Draw a card, then draw cards equal to the number of cards named Sea Cache in your graveyard.

When Sea Hunter enters, you may return target creature with mana value 4 or greater to its owner's hand.

{U}: Sea Strider gets +1/-1 until end of turn.
{U}: Sea Strider gets -1/+1 until end of turn.

Defender
{1}{U}: Sea Wall gets +0/+1 until end of turn.
Whenever Sea Wall perseveres, you may return target creature an opponent controls to its owner's hand. (A creature perseveres when it survives damage.)

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
When Sea's Allure enters, gain control of target creature for as long Sea's Allure remains on the battlefield.

Flash
When Seabreen Nullmage enters, counter target activated or triggered ability. (A triggered ability uses the words “when,” “whenever,” or “at”. Mana abilities can't be targeted.)

When Seafloor Cache enters and when you sacrifice it, create a Treasure token.
{1}{R}, Sacrifice Seafloor Cache: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Seafloor Casket enters and when you sacrifice it, target player mills two cards.
{1}{U}, Sacrifice Seafloor Casket: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Seafloor Shrine enters and when you sacrifice it, create a 1/1 white Merfolk creature token.
{1}{W}, Sacrifice Seafloor Shrine: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Seafloor Tomb enters and when you sacrifice it, exile up to two target cards from graveyards.
{1}{B}, Sacrifice Seafloor Tomb: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Seafloor Wreckage enters and when you sacrifice it, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
{1}{G}, Sacrifice Seafloor Wreckage: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

{2}{W}, {T}: Target creature gets +2/+2 and gains first strike until end of turn.

Seafoam Slasher gets +1/+1 and has deathtouch as long seven or more cards are in your graveyard.
Cycling {2} ({2}, Discard this card: Draw a card.)

Flash
{U}, Sacrifice Seal of Approval: Counter target spell unless its controller pays {2}.