msem-instigator

Target player gains X life.

When Street Performer enters, create a 2/1 blue Illusion creature token with “When this creature becomes the target of a spell or ability, sacrifice it.”

Menace
Deploy 4 (As this enters, you may tap any number of other creatures you control with total power 4 or more.)
When Street Raider enters deployed, discard your hand, then draw three cards.

Ward {1}
Streetslipper can't be blocked.
Whenever you foretell a card or cast a foretold spell, put a +1/+1 counter on Streetslipper.

Whenever you cast a spell, if it isn't your main phase, scry 1.

Strident Retainer's power and toughness are each equal to the number of creatures you control.
Art of war — At the beginning of your end step, if Strident Retainer dealt damage to an opponent this turn, create a 1/1 colorless Samurai creature token.

Destroy target non-Assassin, non-Ninja, non-Rogue creature.

You may have Strikebreaker enter as a copy of a non-Aura enchantment you control, except it's a 2/2 Construct Actor creature in addition to its types.

Target creature gets +2/+1 and gains trample until end of turn. Create a tapped Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Counter target noncreature spell unless its controller pays {1}.
If you control a creature with power 4 or greater, counter that spell instead.

Prowess
Art of war — At the beginning of your end step, if Student of Shigure dealt damage to an opponent this turn, you may draw a card, then discard a card.

Whenever Student of Winds attacks, upgrade target attacking creature. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Flying

Improve {G} ({G}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever an Elf you control dies, you may search your library for a land card, reveal it, put it into your hand, then shuffle.

If you've lost life this turn, you may cast this spell as though it had flash.
Return X target cards with different mana values from your graveyard to your hand. Put Studies Past on the bottom of its owner's library.

Investigate ten times. (Create ten colorless Clue artifact tokens with “{2}, Sacrifice this artifact: Draw a card.”)

Reveal the top four cards of your library. You may put one into your hand and the rest into your graveyard.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

At the beginning of combat on your turn, if you control six or more lands, put a +1/+1 counter on target creature you control.

Concord — At the beginning of combat on your turn, if there are four or more card types among permanents you control, Sturdyshell Hammerclaw gets +2/+1 and gains trample until end of turn.

Flying
{B}, Sacrifice another creature: Draw a card.

({T}: Add {B}.)
As Stygian Dunes enters, you may pay 1 life. If you don't, Stygian Dunes enters tapped.

When Stygian Leviathan enters, target opponent loses life equal to the number of Curses attached to them and you gain that much life.

This spell costs {1} less to cast for each Horror you control.
Exile up to one target non-Horror creature.
Coalesce {7}{W} (You may cast this from your graveyard for {7}{W}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Gain control of target noncreature permanent.
Coalesce {8}{U}{U} (You may cast this from your graveyard for {8}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Once each turn, when you discard a card, you may draw a card.
{1}, Discard a card: Substack Smuggler can't be blocked until end of turn.

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, Substack Sniper deals 1 damage to you and to each cursed opponent.