msem-instigator

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}.

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.

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.)

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.)

{U}, Sacrifice Seal of Insights: Look at the top four cards of your library. Put one into your hand and the rest on the bottom of your library in any order.

Sear Flesh deals 3 damage to target creature or planeswalker. If you've cast another spell this turn, it deals 5 damage instead.

Choose one —
• Destroy target artifact or enchantment.
• Target creature you control explores twice. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then you may put that card in your graveyard.)

Reveal the top five cards of your library. You may put an instant or sorcery card from among them into your hand. Put the rest into your graveyard.

Target creature gains winnow until end of turn if you attacked this turn. Searing Insult deals 2 damage to that creature. (Damage dealt to it also causes its controller to lose that much life.)

Reverberate {3}{R} (When you cast this spell, copy it if you paid its reverberate cost. You may choose new targets for the copy.)
Searing Pulse deals 2 damage to any target.

Haste
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.)

Seaside Skimmer can't be blocked if you've cast a Dragon spell or Adventure spell this turn.

{3}{G}: Seasoned Farmer gets +2/+2 until end of turn.

Whenever Seasoned Lookout deals combat damage to a player, it voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Seasoned Lookout phases in, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put it into your hand.

Search your library for up to four basic land cards with different names, reveal them, put them into your hand, then shuffle.