As long as you have more cards in hand than each opponent, Okina Nightwatch gets +3/+3.

At the beginning of combat on your turn, Oko, the Ringleader becomes a copy of up to one target creature you control until end of turn, except he has hexproof.

+1: Draw two cards. If you've committed a crime this turn, discard a card. Otherwise, discard two cards.

−1: Create a 3/3 green Elk creature token.

−5: For each other nonland permanent you control, create a token that's a copy of that permanent.

+2: Create a Food token. (It's an artifact with ", , Sacrifice this artifact: You gain 3 life.")

+1: Target artifact or creature loses all abilities and becomes a green Elk creature with base power and toughness 3/3.

−5: Exchange control of target artifact or creature you control and target creature an opponent controls with power 3 or less.

Flying

At the beginning of each end step, if a creature died this turn, create a Food token. (It's an artifact with ", , Sacrifice this artifact: You gain 3 life.")

, Sacrifice another creature or artifact: Old Flitterfang gets +2/+2 until end of turn.

You may choose not to untap Old Man of the Sea during your untap step.

: Gain control of target creature with power less than or equal to Old Man of the Sea's power for as long as Old Man of the Sea remains tapped and that creature's power remains less than or equal to Old Man of the Sea's power.

When you cast this spell, reveal cards from the top of your library until you reveal X creature cards. Put all creature cards revealed this way into your graveyard, then put the rest on the bottom of your library in a random order.

Old Stickfingers's power and toughness are each equal to the number of creature cards in your graveyard.

Old-Growth Grove enters tapped.

: Add or .

Trample

Whenever Oliphaunt attacks, another target creature you control gets +2/+0 and gains trample until end of turn.

Mountaincycling (, Discard this card: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.)

Menace

Whenever Olivia's Attendants deals damage, create that many Blood tokens. (They're artifacts with ", , Discard a card, Sacrifice this artifact: Draw a card.")

: Olivia's Attendants deals 1 damage to any target.

Each non-Vampire creature gets -X/-X until end of turn, where X is the number of Vampires you control.

Each opponent exiles a creature with the greatest power among creatures that player controls.

Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, Olórin's Searing Light deals damage to each opponent equal to the power of the creature they exiled.

When Oltec Archaeologists enters, choose one —

• Return target artifact card from your graveyard to your hand.

• Scry 3. (Look at the top three cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Whenever you cast a creature spell, choose one —

• Create a 1/1 colorless Gnome artifact creature token.

• Create a token that's a copy of target artifact token you control.

Flash

When Omen of the Dead enters, return target creature card from your graveyard to your hand.

, Sacrifice Omen of the Dead: Scry 2.

Flash

When Omen of the Hunt enters, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

, Sacrifice Omen of the Hunt: Scry 2.

Flash

When Omen of the Sun enters, create two 1/1 white Human Soldier creature tokens and you gain 2 life.

, Sacrifice Omen of the Sun: Scry 2.

Vanishing 4 (This land enters the battlefield with four time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

: Add , , or .

: Add .

, , Exile Ominous Cemetery: Target creature's owner shuffles it into their library.

When Ominous Traveler enters the battlefield, draft a card from Ominous Traveler's spellbook. That card perpetually gains "You may spend mana as though it were mana of any color to cast this spell" and "When you cast this spell, return a creature named Ominous Traveler you control to its owner's hand."

When Omnath, Locus of Creation enters, draw a card.

Landfall — Whenever a land you control enters, you gain 4 life if this is the first time this ability has resolved this turn. If it's the second time, add . If it's the third time, Omnath deals 4 damage to each opponent and each planeswalker you don't control.

Landfall — Whenever a land you control enters, create a 5/5 red and green Elemental creature token.

Whenever Omnath, Locus of Rage or another Elemental you control dies, Omnath deals 3 damage to any target.

Changeling

Omnipresent Impostor has all card names.

As you search your library for one or more cards, you may choose Omnipresent Impostor as one of those cards. (For example, if you search for two land cards, you may find Omnipresent Impostor and a land card.)

Delirium — Whenever Omnivorous Flytrap enters or attacks, if there are four or more card types among cards in your graveyard, distribute two +1/+1 counters among one or two target creatures. Then if there are six or more card types among cards in your graveyard, double the number of +1/+1 counters on those creatures.

Creatures you control get +2/+1 until end of turn. Investigate. (Create a Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card.")

Enchant snow land you control

When On Thin Ice enters, exile target creature an opponent controls until On Thin Ice leaves the battlefield.

Creatures can't attack planeswalkers you control unless their controller pays for each creature they control that's attacking a planeswalker you control.

, Exile Onakke Oathkeeper from your graveyard: Return target planeswalker card from your graveyard to the battlefield.

Exile all permanents and all cards from all graveyards. Each player shuffles their hand into their library, then draws seven cards. Each player's life total becomes 10. Exile Once More with Feeling.

DCI ruling — A deck can have only one card named Once More with Feeling.

When Ondu Giant enters, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Lifelink

Whenever another modified creature you control dies, put two +1/+1 counters on Ondu Knotmaster.

Spree (Choose one or more additional costs.)

+ — Return target creature card from your graveyard to the battlefield.

+ — Return target Mount or Vehicle card from your graveyard to the battlefield.

+ — Return target Aura or Equipment card from your graveyard to the battlefield attached to a creature you control.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)

I — The Ring tempts you, then each player mills cards equal to your Ring-bearer's power.

II — Destroy all nonlegendary creatures.

III — Each opponent loses 1 life for each creature card in that player's graveyard.

You lose the game.

Discard your hand.

Draw cards equal to the highest mana value among artifacts you control.

Enchant creature or enchantment

Enchanted permanent is an enchantment and loses all other card types. (It still has its abilities, but it's no longer a creature.)

Whenever one or more creatures you control deal combat damage to a player, investigate. (Create a Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card.")

, Exile a creature card from your graveyard: Investigate. You gain 2 life.

Whenever you cast a creature spell, tap target creature.

Target creature gets +X/+0 until end of turn, where X is its power.

Whenever a player casts a black spell, you may pay . If you do, untap target permanent.

Defender, flying

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

When an opponent casts a creature spell, if Opal Caryatid is an enchantment, Opal Caryatid becomes a 2/2 Soldier creature.

When an opponent casts a creature spell, if Opal Titan is an enchantment, Opal Titan becomes a 4/4 Giant creature with protection from each of that spell's colors.

Search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.

Whenever a nontoken creature you control dies, create a 2/2 black Zombie creature token.

Return all artifact and enchantment cards from all graveyards to the battlefield under their owners' control. (Auras with nothing to enchant remain in graveyards.)

: Opportunist deals 1 damage to target creature that was dealt damage this turn.

Target player draws four cards.

Flash

You control your opponents while they're searching their libraries.

While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

Whenever you crank Optical Optimizer, until end of turn, target creature becomes an artifact in addition to its other types and gains ": Draw a card."

Living metal (During your turn, this Vehicle is also a creature.)

Trample

Whenever you attack, bolster 2. The chosen creature gains trample until end of turn. When that creature deals combat damage to a player this turn, convert Optimus Prime.