msem-instigator

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

Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

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.)

Destroy target attacking or blocking creature.

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

Vigilance, lifelink

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.)

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

Prowess
Foresight — When Outpost Merchant enters, if you've drawn two or more cards this turn, create two 1/1 white Bird creature tokens with flying.

Prowess
Whenever Outsider Alchemist deals combat damage to a player, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

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

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}.”

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

Target creature gets +2/+1 and gains haste until end of turn.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Target player reveals their hand. You choose a nonland card from it. That player discards that card unless they discard three other cards.

{G}, Tap an untapped Nymph you control: Overgrown Beast gets +2/+2 until end of turn.

When Overgrowth Guardian enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

Each player discards two cards. Then if there are four or more card types among cards in your graveyard, create two 1/1 white Human creature tokens.

Overkill deals 4 damage to any target that was dealt damage this turn.

Whenever you sacrifice a permanent, Overseer of Armies deals 1 damage to each opponent and each battle they protect.

Target opponent reveals their hand. You may choose a noncreature, nonland card from it. If you do, that player discards that card. Otherwise, they lose 3 life.