msem-instigator

This spell costs {X} less to cast, where X is the greatest power among creatures you controlled that died this turn.
Flash
Flying, trample

When Nidohagane Warfans enters, if it's not a token, create a token that's a copy of it.
Equipped creature gets +1/+0.
Equip {1}

When Night Howlers enters, target opponent reveals three cards from their hand and you choose one of them. Exile that card until Night Howlers leaves the battlefield.

Enchant player
At the beginning of enchanted player's end step, they lose 2 life unless they discard a card.

Flying (This creature can't be blocked except by creatures with flying or reach.)
{B}: Night Screecher gains deathtouch until end of turn. (Any amount of damage this deals to a creature is enough to destroy it.)

When Night Shepherd enters, return a creature you control to its owner's hand.

At the beginning of your upkeep, if there are no noncreature cards in your graveyard, you may return target creature card from your graveyard to the battlefield.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Each player discards a card or sacrifices a creature.
III — Each opponent loses life equal to the number of creature cards in their graveyard. You gain life equal to the number of creature cards in your graveyard.

{1}{G}: Night's Guard gets +2/+2 until end of turn. Activate only once each turn.

Flying
Whenever an opponent discards a card, put a +1/+1 counter on Nightbane Specter.
Whenever Nightbane Specter deals combat damage to a player, that player discards a card.

Flying (This creature can't be blocked except by creatures with flying or reach.)
As long as Nightclad Stalker is enchanted, it gets +1/+0 and has deathtouch and lifelink.

Sacrifice a creature: Look at the top card of target player's library. You may have that player put that card into their graveyard.

Deception {1}{B} ({1}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Nightfall Infiltrator deals combat damage to a player, that player discards a card.

Flying, lifelink
Whenever Nightfall Sphinx or another creature you control enters, each opponent loses 1 life and you gain 1 life.

Whenever you cast a spell, Nightfire Adept gets +3/+0 until end of turn if that spell has the same name as a card in your graveyard.

Whenever Nightly Herald attacks, it deals damage to the defending player equal to the number of Wolves and Werewolves you control.

Whenever a creature deals combat damage to you, that creature's controller gains control of Nightmare Alley.
{T}: Add {C}.
{1}, {T}: Target attacking creature gets +1/+0 until end of turn and can't be blocked this turn.

Whenever a storied permanent you control enters, each opponent discards a card. (Enchantments and legendary permanents are storied.)

Flash
Flying
Whenever a player discards a card, you draw a card. This ability triggers only once each turn.

At the beginning of your upkeep, if Nightmare Riders is in your graveyard, you may mill two cards.

Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] You gain 1 life.
[Lore III] Target creature you control gains first strike until end of turn.

{1}, Discard a card: Create a Gold token. (It's an artifact with “Sacrifice this artifact: Add one mana of any color.”)
{T}, Sacrifice an artifact: Draw a card.

{B}, Discard a card: Post a bounty on target creature. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)

Other Rogues you control have menace.
{2}{U}: Target blocking creature gets -1/-0 until end of turn.