msem-instigator

When Memento Gorgon enters, mill X cards, where X is your devotion to black. Then return a card milled this way to your hand. You lose 1 life. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Enchant creature
When Mantle of the Returned enters, return target creature card from your graveyard to the battlefield. It's a Zombie in addition to its other types.
Enchanted creature gets +1/+1 for each Zombie you control.

Whenever Lampad of Anathemas or another enchantment you control enters, target creature an opponent controls gets -1/-1 until end of turn.

Ward—Pay 2 life. (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays 2 life.)
Heroic — Whenever you cast a spell that targets Hand of Phenax, you draw a card and you lose 1 life. Hand of Phenax gains menace until end of turn.

At the beginning of each end step, if a creature you control died this turn, each opponent loses 2 life.
{3}{B}: Target creature you control gains lifelink until end of turn.

When Grim Procession enters, create two 2/2 black Zombie creature tokens.
{2}{B}: Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Destroy target non-Gorgon creature. Scry 1.

Flash
Flying
{2}{B}, Exile three cards from your graveyard: Create a tapped 2/2 black Zombie creature token.

Return up to two target creature cards from your graveyard to your hand. If you control a creature with power greater than its base power, you gain 3 life.

When Felhide Marauder enters, if you control a creature with power greater than its base power, Felhide Marauder gains haste until end of turn.

Choose one —
• Target opponent reveals their hand. You may choose a creature, enchantment, or planeswalker card from it. That player discards that card.
• Target opponent sacrifices an enchantment.

Whenever Erebos's Whipslang or another enchantment you control enters, each opponent loses 1 life and you gain 1 life.

Enchant creature you control
When Erebos's Benefaction enters, scry 2.
Enchanted creature gets +2/+2 and has menace.

All creatures get -2/-2 until end of turn. Scry 1.

Flying, haste
{2}{B}: Devourer of Dread gets +1/+1 until end of turn. If there are three or more creature cards in your graveyard, put a +1/+1 counter on Devourer of Dread instead.

Deathtouch
Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] You may sacrifice another creature. If you do, draw a card.
[Lore III] Remove all lore counters from Astral Leech. Each opponent sacrifices a creature.

When Asphodel Gravedealer dies, choose one —
• Put a +1/+1 counter on target creature you control.
• Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Return target nonland permanent to its owner's hand. Scry 1.

If you've scried this turn, this spell costs {2} less to cast and can't be countered.
Draw two cards.

Colossal 2—{6}{U} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {6}{U} as a sorcery: Put two +1/+1 counters on it if it has none.)
When Titanic Fathomclaw's colossal ability puts one or more counters on it, return target instant or sorcery card from your graveyard to your hand.

Choose one —
• Draw three cards, then discard a card.
• The owner of target nonland permanent puts it on the top or bottom of their library.

{5}{U}{U}: Thassa's Tidebringer can't be blocked this turn. This ability costs {1} less to activate for each creature you control with a counter on it.

Heroic — Whenever you cast a spell that targets Thassa's Shoreguards, tap target creature an opponent controls. It doesn't untap during its controller's next untap step.
Whenever Thassa's Shoreguards deals combat damage to a player, draw a card.

Enchant creature you control
When Thassa's Benefaction enters, scry 2.
Enchanted creature gets +1/+0 and has flying.

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature.
At the beginning of each combat, you may tap or untap another target nonland permanent.
{2}{U}: Create a 1/1 blue Merfolk Rogue creature token with “{T}: Draw a card, then discard a card.”