msem-instigator

Rhapsody {5}{W}{W} (Pay {5}{W}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever Oltenen Paradise-Seeker attacks, up to one target creature's base power and toughness each become equal to Oltenen Paradise-Seeker's power and toughness until end of turn.

When Ominous Presence enters, search your library for a Curse card, reveal it, then shuffle. If it has mana value 4 or less, you may put it onto the battlefield. Otherwise, put it into your hand.
Ominous Presence gets +1/+1 for each Curse attached to your opponents.

Whenever you draw a card, put a +1/+1 counter on Ontarachie Dryad.
Remove a counter from Ontarachie Dryad: Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”

When Ontarachie Emissary leaves the battlefield, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

When Ontarachie Envoy enters, nourish, then germinate. (To nourish, put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token. To germinate, put a +1/+1 counter on a creature you control or create a 1/1 green Saproling creature token.)

Whenever Ontarachie Hunter attacks, each opponent loses 1 life.
At the beginning of your end step, if an opponent has 10 or less life, transform Ontarachie Hunter.

Flying
Spells your opponents cast cost an additional 2 life to cast.

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.

{T}: Add {G}. If you control an attacking creature, add one mana of any color instead.

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.

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

Ward—Pay 2 life.
When Orchid Suit enters, target opponent reveals their hand, then exiles a nonland card of their choice from it until Orchid Suit leaves the battlefield.

Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] You may discard a card. If you do, draw a card.
[Lore III] Create a token that's a copy of another target creature you control, except it has haste. Sacrifice it at the beginning of the next end step.

Flash (You may cast this spell any time you could cast an instant.)
Flying
When Orichi of the Cold Mist enters, exile another target creature you control. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Defender
Whenever another creature you control enters, Orphan of the Nav gets +1/+1 until end of turn and can attack as though it didn't have defender this turn.

Flying
Whenever an opponent casts a spell, counter it unless that player pays {1} for each spell cast before it this turn.

Flash
Flying
When Oshin enters, counter target spell if its mana value is less than or equal to the number of spells you've cast this turn.

Deception {B} ({B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
When Oshiruko Operative enters, target player loses 1 life.

When Oshiruko Purifier enters, create a 2/2 colorless Spirit creature token.
Colorless creatures you control have lifelink.

Oshiruko Whisperwalker can't be blocked except by Rogues.
Whenever a creature is returned to its owner's hand, you may draw a card. If you do, discard a card.

{T}: Add one mana of any color. Spend this mana only to cast a creature spell or activate an ability of a creature.
{5}{W}{U}{B}{R}{G}, Sacrifice Osk, the Maker's Pet: Create Osk Awakened, a legendary 20/20 green Squirrel God creature token with hexproof, trample, and indestructible.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Oslyd Heretic gets +1/+1 as long as you control no other creatures.

{1}{W}, Exile Outcast of the Folded Fan from your graveyard: Create a 1/1 white Bird creature token with flying. Activate only as a sorcery.

Outer Wall Guard enters with a +1/+1 counter on it if you gained life this turn.

Vigilance, lifelink