msem-instigator

Whenever a creature dealt damage by Slave Child this turn dies, you may pay {B}. If you do, transform Slave Child.

Menace

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Slums Thug gets +1/+1 and has menace as long as you've gained life this turn.

When Street Stalker enters the battlefield, target opponent loses 1 life for each creature you control named Street Stalker.

Once each turn, when you search your library, you may add {B}{B}.

Whenever a creature dealt damage by Truth Extractor this turn dies, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Undercity Diplomat can't be blocked by marked creatures.

At the beginning of your upkeep, reveal the top card of your library. If it has the same name as a card in your graveyard, put the revealed card into your hand. Otherwise, put it into your graveyard.

All creatures have “When this creature enters the battlefield, destroy target creature with a lesser mana value.”

{4}{B}{B}: Return Urchin Defector from your graveyard to the battlefield transformed.

Whenever Arisen Rider attacks, creatures your opponents control get -1/-1 until end of turn.
If Arisen Rider or another creature or planeswalker would die, exile it instead.

Target creature gets +2/+2 and gains indestructible until end of turn.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
Whenever a creature enters the battlefield under your control, each opponent loses 1 life.
I, II — Create a 1/1 black Actor creature token with lifelink.
III — Each opponent loses life equal to the number of tokens you control. You gain life equal to the life lost this way.

Non-Actor creatures can't block this turn.

Menace
When Bit Player dies, it deals 1 damage to each opponent.

{4}{R}: Blind Tunneler gets +3/+0 until end of turn.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Bounty Crusher has trample as long as it's being blocked by a marked creature.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature you don't control blocks, Cadalon Chemist deals 1 damage to that creature.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature dies, Diasune Tracker deals 1 damage to target player.

Flameblade deals 4 damage to target player or planeswalker.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
You don't lose unspent red mana as steps and phases end.
I, II — Add {R}{R}.
III — Create a 3/3 red Phoenix creature token with flying, haste, and “{R}: This creature gets +1/+0 until end of turn.”

This spell costs {2} less to cast if a permanent you controlled left the battlefield this turn.
Target creature gets +3/+0 and gains trample until end of turn.

First strike
Whenever you discard a card, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Each player discards their hand, then draws cards equal to the greatest number of cards discarded this way.

When Impatient Busker enters the battlefield, you may put a lore counter on target Saga.