msem-instigator

Enchant opponent
Whenever you attack enchanted player, look at the top X cards of your library, where X is one plus the number of attacking creatures you control. Put one of those cards into your hand and the rest on the bottom of your library in any order.

Enchant opponent
At the beginning of enchanted player's upkeep, they mill two cards.
{U}, Sacrifice Strange Tides: Shuffle up to four target cards from your graveyard into your library.

Tap up to two target creatures. Those creatures don't untap during their controllers' next untap steps. Scry 1.

Enchant opponent
Whenever enchanted player draws a card or casts a spell, put a foreshadow counter on Thalassophobia.
Remove eight foreshadow counters from Thalassophobia and sacrifice it: Create an 8/8 blue Kraken creature token.

{1}{U}: Twilight Privateer voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Twilight Privateer phases in, up to one other target creature voyages.

You may cast up to two target instant and/or sorcery cards from your graveyard this turn. If a spell cast this way would be put into your graveyard, exile it instead.

Whenever Wakeborne Kraken or another Kraken, Leviathan, Octopus, or Serpent you control enters, you may return target creature an opponent controls to its owner's hand.
Whenever a creature an opponent controls leaves the battlefield, if it didn't die, draw a card.

Deathtouch
Abyss Surger enters with X +1/+1 counters on it, where X is the greatest power among creature cards in your graveyard.

As an additional cost to cast this spell, sacrifice a creature or pay {3}.
Destroy target creature with power 3 or less.

{2}{B}, Sacrifice a creature: Draw a card. You gain 1 life.

Look at the top four cards of your library. Put any number of them into your graveyard and the rest on top of your library in any order.
You draw two cards and you lose 2 life.

As an additional cost to cast this spell, sacrifice a creature.
Return a creature card from your graveyard to the battlefield, then return another creature card from your graveyard to your hand.

Menace
Whenever you sacrifice an artifact or creature, Crain's Crew gets +1/+1 until end of turn.

Whenever Crain's Crony enters or attacks, reveal the top card of your library and put it into your hand. You lose life equal to that card's mana value.
At the beginning of each end step, if you didn't lose life this turn, you lose the game.

Flash

Enchant opponent
When Down with the Ship enters, enchanted player discards a card unless they sacrifice a creature.
{1}{B}, Sacrifice Down with the Ship: Return target creature card from your graveyard to your hand.

This spell costs {1} less to cast for each card put into your graveyard from anywhere this turn.
At the beginning of each player's upkeep, that player loses 1 life, discards a card, and sacrifices a creature.

When Dusk Lieutenant enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)
Once each turn, when you discard a card during your turn, each opponent discards a card.

Exile target creature or planeswalker with mana value 4 or less.

When Faithless Deserter enters, you may sacrifice a creature. If you do, each opponent sacrifices a creature.

Menace
As long as you control exactly one other creature, that creature gets +1/+1 and has menace.

Enchant opponent
At the beginning of enchanted player's upkeep, they lose 1 life and each of their opponents gains 1 life.
{4}{B}, Sacrifice Forsaken Shores: Enchanted player loses 3 life and you gain 3 life.

Deathtouch
When Ghastly Scorpion dies, you draw a card and you lose 1 life.

This spell costs {1} less to cast for each card put into your graveyard from anywhere this turn.
Target creature gets -4/-4 until end of turn.

{1}{B}, Discard a card: Exile target creature card from your graveyard. Create a token that's a copy of that card, except it's a 5/5 black Horror.