When Oasis Gardener enters the battlefield, you gain 2 life.

: Add one mana of any color.

When Oath of Jace enters the battlefield, draw three cards, then discard two cards.

At the beginning of your upkeep, scry X, where X is the number of planeswalkers you control.

When Oath of Liliana enters the battlefield, each opponent sacrifices a creature.

At the beginning of each end step, if a planeswalker entered the battlefield under your control this turn, create a 2/2 black Zombie creature token.

Equipped creature gets +3/+1.

Whenever equipped creature dies, return that card to the battlefield under your control if it's a Samurai card.

When Oathkeeper, Takeno's Daisho is put into a graveyard from the battlefield, exile equipped creature.

Equip

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.)

+1: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life.

−2: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."

−7: Target player draws seven cards and loses 7 life.

: Add , , or .

: Add , , or .

: Add , , or .

The owner of target nonland permanent shuffles it into their library, then draws two cards.

, : Put a fate counter on target permanent.

, , Sacrifice Oblivion Stone: Destroy each nonland permanent without a fate counter on it, then remove all fate counters from all permanents.

Choose one —

• Return target multicolored permanent card with mana value 3 or less from your graveyard to the battlefield tapped.

• Counter target instant or sorcery spell.

• Destroy target creature or planeswalker with mana value 3 or less.

When Obscura Polymorphist enters the battlefield, exile target creature. Its controller seeks a creature card.

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.)

Vigilance

Enchanted creature gets +2/+2 and has vigilance.

Equipped creature gets +2/+1 and has haste.

Whenever a Warrior creature enters the battlefield, you may attach Obsidian Battle-Axe to it.

Equip

When Odric, Blood-Cursed enters the battlefield, create X Blood tokens, where X is the number of abilities from among flying, first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance found among creatures you control. (Count each ability only once.)

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

I — Put a +1/+1 counter on up to one target creature. Create a Food token.

II — Draw a card. Create a Food token.

III — Create a 1/1 white Halfling creature token for each Food you control.

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 the battlefield.)

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

Whenever Ohran Viper deals combat damage to a creature, destroy that creature at end of combat.

Whenever Ohran Viper deals combat damage to a player, you may draw a card.

Tap target creature. It doesn't untap during its controller's next untap step.

Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

White creature spells you cast cost less to cast.

Whenever you cast a creature spell, create a 1/1 white Warrior creature token with vigilance.

Flying

When Old Rutstein enters the battlefield and at the beginning of your upkeep, mill a card. If a land card is milled this way, create a Treasure token. If a creature card is milled this way, create a 1/1 green Insect creature token. If a noncreature, nonland card is milled this way, create a Blood token.

Flying

Whenever another creature enters the battlefield under your control, you may discard a card. If you do, put a +1/+1 counter on that creature, it gains haste until end of turn, and it becomes a Vampire in addition to its other types.

Flash

When Omen of the Hunt enters the battlefield, 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.

When Ominous Roost enters the battlefield and whenever you cast a spell from your graveyard, create a 1/1 blue Bird creature token with flying and "This creature can block only creatures with flying."

Target creature gets +2/+2 until end of turn. Untap it. (Then exile this card. You may cast the creature later from exile.)

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.

Enchant creature

At the beginning of your upkeep, sacrifice a creature.

Enchanted creature gets +3/+3 and has trample.

Enchanted creature is a Demon Spirit.

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

Target player draws a card.

Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

When you have 10 or less life, if Opal Avenger is an enchantment, Opal Avenger becomes a 3/5 Soldier creature.

When an opponent casts a creature spell, if Opal Guardian is an enchantment, Opal Guardian becomes a 3/4 Gargoyle creature with flying and protection from red.

All Slivers have "Whenever this permanent becomes the target of a spell an opponent controls, you may draw a card."

Open Fire deals 3 damage to any target.

Whenever Ophidian attacks and isn't blocked, you may draw a card. If you do, Ophidian assigns no combat damage this turn.

At the beginning of each upkeep, if you control no Snakes, create a 1/1 black Snake creature token with deathtouch.

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.

Counter target spell unless its controller pays for each card in your hand.

When Oran-Rief Ooze enters the battlefield, put a +1/+1 counter on target creature you control.

Whenever Oran-Rief Ooze attacks, put a +1/+1 counter on each attacking creature with a +1/+1 counter on it.

Permanents enter the battlefield tapped.

Orchard Spirit can't be blocked except by creatures with flying or reach.

, Sacrifice a creature: Orcish Bloodpainter deals 1 damage to any target.

: Orcish Cannoneers deals 2 damage to any target and 3 damage to you.

, Sacrifice an artifact: Orcish Mechanics deals 2 damage to any target.

When Orcish Paratroopers enters the battlefield, flip it from a height of at least one foot. Sacrifice Orcish Paratroopers unless it turns over completely at least once during the flip and lands face up.

Orcish Veteran can't block white creatures with power 2 or greater.

: Orcish Veteran gains first strike until end of turn.

, Pay 1 life: Counter target black spell.

When this creature enters the battlefield, you may exile target non-Horse creature you control that wasn't put onto the battlefield with this ability this turn, then return it to the battlefield under its owner's control.