msem-instigator

Until end of turn, target creature you control gets +2/+0 and gains “When this creature dies, mill two cards, then return it to the battlefield under its owner's control.”

Haste
Ruin Shark attacks each turn if able.
Ruin Shark gets +1/+0 and has first strike as long as you've drawn two or more cards this turn.

You have hexproof.
Creatures you don't control have base power and toughness 1/1 and lose all abilities.
Nonbasic lands you don't control don't untap during their controller's untap step.

When Rum Guzzler enters, forebode, then you lose 1 life. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Target creature you control gets +1/+1 until end of turn. It deals damage equal to its power to target creature you don't control.
Madness {3}{G} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Rustshell Crustacean gets +1/+1 for each artifact you control.
Whenever Rustshell Crustacean attacks, choose one —
• Search your library for an Equipment card, reveal it, and put it into your hand, then shuffle.
• Create a Treasure token.

When Sadistic Indulgence enters, create three 1/1 white Human creature tokens with “This creature can't attack or block.”
Pay 1 life: Destroy target nonland permanent you control.

Choose one —
• Tap target creature.
• Untap target creature and remove it from combat.
Draw a card.

When Salty Swab enters, exile the top three cards of your library.
Resolute — You may play cards exiled with Salty Swab as long as Salty Swab's power is greater than its base power.

[+1]: Scry 1, then draw a card. You lose 1 life.
[–2]: Target player sacrifices a creature, then loses life equal to the greatest power among creatures they control.
[–5]: Choose a nonland card name. Exile all creatures and planeswalkers with that name, then search target player's graveyard, hand, and library for any number of cards with that name and exile them. That player shuffles.

You may sacrifice three artifacts rather than pay this spell's mana cost.
Exile three artifact cards from your graveyard: Return Salvage Titan from your graveyard to your hand.

Flying
Whenever you cast an artifact or enchantment spell, tap target artifact or creature an opponent controls. It doesn't untap during its controller's next untap step.

Destroy target land. Its controller creates a colorless Desert land token with “{T}: Add {C}.”

As long as you control exactly two creatures, those creatures get +2/+1 and have lifelink.

Enchant player
Whenever enchanted player taps a nonbasic land they control, that land doesn't untap during its controller's next untap step.

Schoolmaster gets +1/+1 for each other Merfolk you control.
When Schoolmaster enters, create a 1/1 white Merfolk creature token.

Menace (This creature can't be blocked except by two or more creatures.)
Whenever another creature dies, you may salvage a creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

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.)

{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.

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.