msem-instigator

Opera House enters tapped.
When Opera House enters, add one mana of any color.
{T}, Sacrifice Opera House: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Scry 1.
Draw a card.

Whenever you make first contact, Oscuran Wingmate gains flying until end of turn. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)

All creatures able to block Osheen Courtier do so.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

When Ostracizer Orb enters, exile target nonartifact, nonland permanent until Ostracizer Orb leaves the battlefield.

Enchant player
At the beginning of enchanted player's upkeep, they tap an untapped creature they control.

Enchant player
Whenever enchanted player becomes the target of a spell or ability they don't control, if it isn't a copy, its controller copies it.

Hexproof
When Overburdened Trader enters, create three 1/1 colorless Construct artifact creature tokens.

Counter target spell. For each other card named Overcharge in your graveyard, create a colorless Canister artifact token with “{T}, Sacrifice this artifact: Add {C}.”

Lifelink
When Pact Equivocator enters, you lose 2 life and draw a card.

When Paint by Numbers enters, put up to ten brush counters on it.
Whenever a player casts a instant or sorcery spell with mana value equal to the number of brush counters on Paint by Numbers, remove a brush counter from it and copy that spell. You may choose new targets for the copy. Then sacrifice Paint by Numbers if it has no brush counters.

{2}, {T}, Sacrifice Pale Morningstar Powder: Put two -1/-1 counters on target creature.

Creatures you control with +1/+1 counters on them have haste and trample.
At the beginning of combat on your turn, target creature explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then you may put that card into your graveyard.)

Creatures your opponents control enter tapped.
{7}{W}: Tap all creatures target player controls.

Whenever Path Lighter deals combat damage to a player, it explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Create two tapped Treasure tokens. (Then exile this card. You may cast the creature later from exile.)

Exile two cards from your graveyard: Petrified Guard becomes a 3/1 Zombie creature until end of turn.

Codex — Eleventh Hour Breakthrough; Mentorb; Ostracizer Orb; Possibility Engine; Sealed Riftway; Self Replication. (As this enters, conjure its contents into a shuffled face-up additional library.)
{T}, Sacrifice an artifact: Draw a card from the codex's library.

[+1]: Artifact creatures you control get +1/+1 and gain haste until end of turn.
[–X]: You may cast an artifact card with mana value X or less from your hand without paying its mana cost. If it has {X} in its cost, {X} is X.
[–6]: Choose a number. For each artifact you control with the mana value equal to the chosen number, create a token that's a copy of it.

Target creature you control deals damage equal to its power to any target. Then put a -1/-1 counter on that creature.

Flying
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Deathtouch
Unveil {3}{B}{G} ({3}{B}{G}: Transform this. Unveil only as a sorcery.)

Vigilance, deathtouch, menace

Advance {3}{W} (Cast this for {3}{W} to advance it as it enters. {3}{W}: Advance this as a sorcery.)
At the beginning of your upkeep, you gain 1 life.
Whenever Plush Tea Party advances, create a token that's a copy of it.

Target creature gets -3/-3 until end of turn. You gain 3 life. (Then exile this card. You may cast the creature later from exile.)