msem-instigator

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 {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.

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.

Deception {2}{U} ({2}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
When Oshiruko Silencer enters, return target creature to its owner's hand.

Out-of-Depth Amateur can't attack or block alone.
Attain {4}{R} ({4}{R}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

{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.

Outfitted Ibex has menace as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Flash
When Outland Alchemist enters, return another permanent you control to its owner's hand.

Outlands Bodyguard can't attack alone.
You may exert Outlands Bodyguard as it attacks. When you do, it must be blocked this turn if able. (An exerted creature won't untap during your next untap step.)

Lifelink
Outskirts Provider enters with a +1/+1 counter on it if a creature attacked this turn and wasn't blocked.

When Overconfident Batter dies, if it's enchanted or you cast a spell that targeted it this turn, you gain 3 life.

Overgrown Enclave enters tapped.
{T}: Add {G} or {U}.
{4}{G}{U}: Until end of turn, Overgrown Enclave becomes a Turtle creature with ward {2} in addition to its other types.
Scavenge {5}{G}{U}

Overgrown Siren must be blocked if able.

Flash
Flying
Whenever you cast another spell with flash or an instant, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Vigilance
When Paired Pathfinders enters, if three or more colors were spent to cast it, create a 1/1 colorless Servo artifact creature token.

Whenever a creature dies, Pakka, the Shadowcloak deals 1 damage to each opponent.

When Pale Night Remnants enters, return up to one target nonland permanent and all other permanents with the same name as that permanent to their owners' hands.

Once during each of your turns, you may cast a legendary creature or planeswalker spell from your graveyard.
Sacrifice Pallid Herald: Exile up to three target cards from graveyards.

Other creatures you control get +1/+0.
{R}{W}: Create a 1/1 red and white Warrior creature token. That token gains haste. Exile it at the beginning of the next end step. Activate only as a sorcery.

When Pantheon Breaker enters, each opponent sacrifices an enchantment.

Flash
As long as Panya and exactly one other creature are attacking, both have flying.

Whenever Panya attacks, you may put an escapade counter on her, then you may cast an instant or sorcery card from your hand with mana value equal to the number of escapade counters on Panya without paying its mana cost.
{1}{U}: Panya gains flying until end of turn.

Whenever Paomar Greatheart attacks, put a trample counter on target attacking creature in its pack. (Two or more creatures you control with equal power are in a pack.)