msem-instigator

Search your library for a creature or sorcery card, put it into your graveyard, then shuffle.
Reconstruct {2}{B} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Converge — When Operations Manager enters, create X 1/1 colorless Servo artifact creature tokens, where X is the number of colors of mana spent to cast Operations Manager.

Lifelink
Whenever Operative BABY attacks or you cast a black or red spell, create a 1/1 blue Elemental creature token with flying.

Menace
Whenever Operative GINGER attacks or you cast a blue or white spell, Operative GINGER deals 1 damage to any target.

Flash
Whenever Operative POSH attacks or you cast a green or red spell, exile up to one target nontoken permanent. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Deathtouch
Whenever Operative SCARY attacks or you cast a green or white spell, you may draw a card. If you do, you lose 2 life.

Ward {3}
Whenever Operative SPORTY attacks or you cast a blue or black spell, put a +1/+1 counter on Operative SPORTY.

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Ophelia's Neophyte enters, you may have another target creature you control gain lifelink until end of turn.

Once each turn, you may pay {U} rather than pay the mana cost for a blue spell you cast.

When Ophorio Scavenger enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Ophorio Scavenger gets +1/+1 as long as you control three or more artifacts.

Voracious 2 (As this enters, you may sacrifice up to two artifacts and/or creatures. This creature enters with that many +1/+1 counters on it.)
When Opportunistic Beast enters, destroy up to one target creature that was dealt damage this turn.

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, if it's your main phase, after this phase, there is an additional combat phase followed by an additional main phase.

Enchant creature
Enchanted creature can't attack or block unless its controller pays {3}.
Activated abilities of enchanted creature cost {3} more to activate.

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

Whenever Optimistic Chronicler deals damage to a player or noncreature permanent, surveil 1, then draw a card.

Whenever you cast your first instant or sorcery spell each turn, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

When Opulent Proprietor enters, you may search your library and/or graveyard for an Aura, Aurashaper, Equipment, or Vehicle card, reveal it, and put it into your hand. If you search your library this way, shuffle.

Draw three cards, then discard two cards.

When Oracle Crab enters, scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Whenever Oracle of Flames becomes tapped, up to one target creature you control gets +2/-2 until end of turn.

Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on Oracle of Tides.

Menace
At the beginning of your end step, if a player lost 3 or more life this turn, put a +1/+1 counter on target Azra or Demon you control.

Search your library for up to six cards and exile them face down. Shuffle, then draw a card.

Enchant creature
Enchanted creature gets -3/-3.
When enchanted creature dies, its controller may scry 1.

Whenever another nonland permanent you control enters, return that permanent to its owner's hand at the beginning of the next end step.