msem-instigator

({T}: Add {U} or {B}.)
Whenever Murmuring Falls becomes tapped, you lose 1 life unless you control two or more basic lands.

Whenever a creature you control dies, destroy target creature you don't control.

Whenever a player casts a spell, that player exiles the top card of each library face down.
Each player may look at and play cards they exiled with Mystic of Many Winds.

Vigilance, deathtouch
Prevent all damage that would be dealt to Nataila, Raven's Repented while it's attacking or blocking alone.

Choose a creature card name. Each player sacrifices a creature, then each player who controls a creature with the chosen name gets a poison counter.
Draw a card.

At the beginning of each player's upkeep, Noble's Hedonism deals 1 damage to that player, then that player exiles the top card of their library. Until end of turn, they may play that card.

({T}: Add {B} or {G}.)
Whenever Nomad's Township becomes tapped, you lose 1 life unless you control two or more basic lands.

When Nomadic Patriarch enters the battlefield, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)
Remove a +1/+1 counter from Nomadic Patriarch: Put a +1/+1 counter on each other creature token you control.

Target opponent takes an extra turn after this one. Until your next turn, you control that player during extra turns.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

You may cast Oil the Mind from your graveyard.
Target player mills three cards.
If Oil the Mind was cast from your graveyard, conjure a card named Fatigue and put it on top of your library. (It's a colorless sorcery that costs {2} with “Draw a card.”)

Target creature gets -X/-X until end of turn, where X is the number of enchantments you control.

This spell costs {G} less to cast if it targets a blue or black permanent.
Destroy target artifact, enchantment, or planeswalker.

This spell costs {1}{B} less to cast if it targets a green or white permanent.
Destroy target creature or planeswalker.

This spell costs {1}{U} less to cast if it targets a red or green spell.
Counter target spell.
Draw a card.

This spell costs {R} less to cast if it targets a white or blue permanent.
Once Scarred deals 4 damage to target creature or planeswalker.

This spell costs {W} less to cast if it targets a black or red permanent.
Exile target nonland permanent with mana value 3 or less.

When Ophidian Oracle enters the battlefield, draw a card, then abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
Recite {2}{G}{G} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters the battlefield or if it would leave the battlefield.)

Bleed {1}{B/R} (You may cast this spell for its bleed cost if an opponent has lost life this turn.)
Haste
When Opportunistic Raiders enters the battlefield, if it's your main phase, after this phase, there is an additional combat phase followed by an additional main phase.

Creatures can't attack you unless their controller pays {3} for each of those creatures.

When Oracle of Edicts enters the battlefield, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an Aura enters the battlefield under your control, scry 1.

Deception {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Oshiruko Conspirator deals combat damage to a player, you may discard a Rogue card. If you do, search your library for an instant or sorcery card, reveal it, put it into your hand, then shuffle.

Enchant player
At the beginning of your upkeep, enchanted player loses 1 life.

When Over the Horizon enters the battlefield, scry 1.
{T}: Add {C}.
{1}, {T}: Return Over the Horizon to its owner's hand.

Enchant creature (Target a creature as you cast this. This card enters the battlefield attached to that creature.)
Enchanted creature can't attack or block.

Bleed {R} (You may cast this spell for its bleed cost if an opponent has lost life this turn.)
Add {R}{R}{R}.