msem-instigator

Whenever a Survivor you control dies, target creature you don't control gets -1/-1 until end of turn.

When Saffrisa's Darkcaster enters, look at the top four cards of your library. You may substantiate a card from among them. Put the rest into your graveyard. (To substantiate a card, put it onto the battlefield face down as a 2/2 creature. You may turn it face up and cast it at any time for its mana cost if it isn't a creature.)

{B}, Pay 1 life: Target creature's controller sacrifices it unless that player pays 1 life.
{B}, Sacrifice a creature: You gain life equal to the sacrificed creature's power.

When Scion of Sarrithaz enters, create a 2/2 black Zombie creature token.
{2}{B}, Sacrifice a creature: Draw a card.

When Scorpid Sniper enters, you may have target creature get -1/-1 until end of turn.

Whenever you cast your second spell each turn, each opponent loses 1 life and you gain 1 life.

Deathtouch
{U/B}: Change a target of target spell or ability that targets Serafina to another creature you control.
Whenever Serafina deals damage to a player, at the beginning of the next end step, that player loses life equal to the life they lost this turn.

Menace
When Setar Ritualist enters or whenever you cast a spell, if {U}{R} was spent to cast it, Setar Ritualist deals 3 damage to target permanent, then tap that permanent. Put a +1/+1 counter on Setar Ritualist.

Lifelink
Whenever an Aura becomes attached to Shrieking Gnoll, put a +1/+1 counter on Shrieking Gnoll, then target creature an opponent controls gets -1/-1 until end of turn for each +1/+1 counter on Shrieking Gnoll.

When Silencing Guardian enters, you may have target creature get -1/-1 until end of turn.

Silent Doom enters tapped.
You may cast Silent Doom from your graveyard as long as you sacrificed a permanent this turn.
Cycling {B} ({B}, Discard this card: Draw a card.)

{2}, Pay 2 life: Silkwrap Brawler gains indestructible until end of turn.

When Specimen Collector enters, 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.)

Flying
Sacrifice a Fungus, Saproling, Plant, or Insect: You gain 2 life.

Creature cards in your graveyard have revive. The revive cost is equal to their mana cost. (Pay that creature's mana cost, Exile that card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
At the beginning of your end step, each cursed opponent loses 1 life. You gain life equal to the life lost this way.

Whenever a storied permanent you control enters, each opponent loses 2 life. (Enchantments and legendary permanents are storied.)

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
At the beginning of your upkeep, if Subturgian Proliferator engorged a creature card, you may pay {3}{B}. If you do, create a black Zombie creature token with power equal to the engorged card's power and toughness equal to that card's toughness.

Deathtouch
Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
Whenever an opponent has less life or fewer cards in their main library than the number of Curses attached to them, they lose the game.

Flash
Cycling {2} ({2}, Discard this card: Draw a card.)

Flying, lifelink
Sacrifice a creature: Until end of turn, Turned Watcher gets +1/+0 and gains “Whenever Turned Watcher deals combat damage to a player, draw a card.”

Menace
Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)

When Undying Watcher enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)
Sacrifice another creature: Undying Watcher gains indestructible until end of turn.

Lifelink
Whenever a creature enters from a graveyard, gain control of that creature.

Lifelink
Whenever Walking Remorse or another creature dies, Walking Remorse deals 1 damage to target player or planeswalker.