Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)

Enchanted creature gets +2/+1.

Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)

Enchanted creature gets +1/+2.

Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)

Enchanted creature gets +3/+1.

During turns other than yours, tapped creatures you control have hexproof.

Enchant creature

Enchanted creature gets +3/+3.

Constellation — Whenever Oakheart Dryads or another enchantment you control enters, target creature gets +1/+1 until end of turn.

At the beginning of each player's upkeep, that player chooses target player who controls more creatures than they do and is their opponent. The first player may reveal cards from the top of their library until they reveal a creature card. If the first player does, that player puts that card onto the battlefield and all other cards revealed this way into their graveyard.

At the beginning of each player's upkeep, that player chooses target player who controls more lands than they do and is their opponent. The first player may search their library for a basic land card, put that card onto the battlefield, then shuffle.

At the beginning of each player's upkeep, that player chooses target player who has more life than they do and is their opponent. The first player may have Oath of Mages deal 1 damage to the second player.

Whenever Oath of the Ancient Wood or another enchantment you control enters, you may put a +1/+1 counter on target creature.

Vigilance

Other creatures you control get +0/+2 and have vigilance.

, : You gain 5 life.

, : Draw a card, then discard a card.

, : Target creature gets -2/-2 until end of turn.

, : Obelisk of Alara deals 3 damage to target player or planeswalker.

, : Target creature gets +4/+4 until end of turn.

: Add , , or .

: Add , , or .

, : Return target permanent you both own and control to your hand.

This spell can't be countered.

Destroy all artifacts, creatures, and lands. They can't be regenerated.

When Oblivion Ring enters, exile another target nonland permanent.

When Oblivion Ring leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Flying

, Return a land you control to its owner's hand: Untap target land.

: Add .

: Return Oboro, Palace in the Clouds to its owner's hand.

Draw a card.

Madness (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Protection from black

: Target creature gains protection from black until end of turn.

: Put a blaze counter on target land without a blaze counter on it. For as long as that land has a blaze counter on it, it has "At the beginning of your upkeep, this land deals 1 damage to you." (The land continues to burn after Obsidian Fireheart has left the battlefield.)

When Obstinate Baloth enters, you gain 4 life.

If a spell or ability an opponent controls causes you to discard Obstinate Baloth, put it onto the battlefield instead of putting it into your graveyard.

When Obzedat, Ghost Council enters, target opponent loses 2 life and you gain 2 life.

At the beginning of your end step, you may exile Obzedat. If you do, return it to the battlefield under its owner's control at the beginning of your next upkeep. It gains haste.

Enchant creature

Enchanted creature has ": Draw a card."

: Enchanted creature gains vigilance until end of turn.

Flip a coin. If it comes up heads, counter target instant or sorcery spell. If it comes up tails, copy that spell and you may choose new targets for the copy.

First strike (This creature deals combat damage before creatures without first strike.)

Whenever Odric, Master Tactician and at least three other creatures attack, you choose which creatures block this combat and how those creatures block.

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Whenever Odylic Wraith deals damage to a player, that player discards a card.

Flash

When Offalsnout leaves the battlefield, exile target card from a graveyard.

Evoke (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

When Ogre Arsonist enters, destroy target land.

Haste

When Ogre Gatecrasher enters, destroy target creature with defender.

Defender

Ogre Jailbreaker can attack as though it didn't have defender as long as you control a Gate.

Whenever Ogre Marauder attacks, it gains "Ogre Marauder can't be blocked" until end of turn unless defending player sacrifices a creature of their choice.

Whenever a player casts a spell, tap Ogre Recluse.

When Ogre Savant enters, if was spent to cast it, return target creature to its owner's hand.

, Discard a card at random: Ogre Shaman deals 2 damage to any target.

Ogre Taskmaster can't block.

Equipped creature gets +5/+0.

Equip

: Target snow creature gains first strike until end of turn. ( can be paid with one mana from a snow source.)

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

Okk can't attack unless a creature with greater power also attacks.

Okk can't block unless a creature with greater power also blocks.

Flying

: Olivia Voldaren deals 1 damage to another target creature. That creature becomes a Vampire in addition to its other types. Put a +1/+1 counter on Olivia Voldaren.

: Gain control of target Vampire for as long as you control Olivia Voldaren.

Players can't draw cards.

At the beginning of each player's draw step, that player exiles the top card of their library. If it's a land card, the player puts it onto the battlefield. Otherwise, the player casts it without paying its mana cost if able.

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

: Target creature becomes a Frog with base power and toughness 3/3 until end of turn.

O-Naginata can be attached only to a creature with power 3 or greater.

Equipped creature gets +3/+0 and has trample.

Equip (: Attach to target creature you control. Equip only as a sorcery.)

Whenever Ondu Cleric or another Ally you control enters, you may gain life equal to the number of Allies you control.