+2: Each opponent loses 1 life. You gain life equal to the life lost this way.

−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.

−8: You get an emblem with ", Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."

Ob Nixilis of the Black Oath can be your commander.

Menace

Whenever Obeka, Splitter of Seconds deals combat damage to a player, you get that many additional upkeep steps after this phase.

: Add , , or .

: Add , , or .

: Add , , or .

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.)

As Obelisk of Urd enters, choose a creature type.

Creatures you control of the chosen type get +2/+2.

When Obscura Storefront enters, sacrifice it. When you do, search your library for a basic Plains, Island, or Swamp card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

If you would draw a card, you may skip that draw instead.

This spell costs less to cast if you control a Human creature and a non-Human creature.

Draw two cards.

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.)

Target creature gains deathtouch and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

This spell costs more to cast for each target beyond the first.

Choose any number of target players. Investigate X times, where X is the total number of creatures those players control.

Ogre Enforcer can't be destroyed by lethal damage unless lethal damage dealt by a single source is marked on it.

Attacking creatures you control have deathtouch.

Whenever a creature you control deals combat damage to a player, draw a card.

Flying, vigilance

Whenever a Dragon you control attacks, tap target nonland permanent an opponent controls. That permanent doesn't untap during its controller's next untap step.

Flying, trample

Whenever O-Kagachi, Vengeful Kami deals combat damage to a player, if that player attacked you during their last turn, exile target nonland permanent that player controls.

: Add .

, : Target legendary creature gets +1/+1 until end of turn.

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.

Flying

Old-Fashioned Vampire gets +2/+2 and has deathtouch as long as it's dark outdoors.

Omarthis, Ghostfire Initiate enters with X +1/+1 counters on it.

Whenever you put one or more +1/+1 counters on another colorless creature, you may put a +1/+1 counter on Omarthis.

When Omarthis dies, manifest a number of cards from the top of your library equal to the number of counters on it.

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.

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.

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.

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

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.

Haste

At the beginning of your upkeep, return a red creature you control to its owner's hand.

, Remove one or more +1/+1 counters from among creatures you control: Create an X/X green Ooze creature token, where X is the number of +1/+1 counters removed this way.

Haste

Tribute 2 (As this creature enters, an opponent of your choice may put two +1/+1 counters on it.)

When Oracle of Bones enters, if tribute wasn't paid, you may cast an instant or sorcery spell from your hand without paying its mana cost.

You may play an additional land on each of your turns.

Play with the top card of your library revealed.

You may play lands from the top of your library.

Flying

When Oracle of the Alpha enters the battlefield, conjure the Power Nine into your library, then shuffle.

Whenever Oracle of the Alpha attacks, scry 1.

Trample

Landfall — Whenever a land you control enters, put a +1/+1 counter on Oran-Rief Hydra. If that land is a Forest, put two +1/+1 counters on Oran-Rief Hydra instead.

When Oran-Rief Ooze enters, 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.

Whenever Oran-Rief Survivalist or another Ally you control enters, you may put a +1/+1 counter on Oran-Rief Survivalist.

As an additional cost to cast this spell, you may reveal a Dragon card from your hand.

Defender, flying

When Orator of Ojutai enters, if you revealed a Dragon card or controlled a Dragon as you cast this spell, draw a card.

, : Add two mana in any combination of colors. Spend this mana only to cast Dragon spells or activate abilities of Dragons.

, , Sacrifice Orb of Dragonkind: Look at the top seven cards of your library. You may reveal a Dragon card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

: Add one mana of any color.

Other noncreature artifacts are mono and continuous. (Each activated ability of mono artifacts costs an additional to activate if its cost doesn't already include . As long as a continuous artifact is tapped, it loses all abilities.)

: Target land becomes a Swamp until its controller's next untap step.

Flying, trample

When Orcus, Prince of Undeath enters, choose one —

• Each other creature gets -X/-X until end of turn. You lose X life.

• Return up to X target creature cards with total mana value X or less from your graveyard to the battlefield. They gain haste until end of turn.

Enchant creature

Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Heliod.

When you sacrifice Ordeal of Heliod, you gain 10 life.

Enchant creature

Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Purphoros.

When you sacrifice Ordeal of Purphoros, it deals 3 damage to any target.

Protection from black

: Order of Leitbur gains first strike until end of turn.

: Order of Leitbur gets +1/+0 until end of turn.

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.)

Flying, lifelink, haste

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)

Other Vampires you control have exalted.

Whenever Order of the Alabaster Host becomes blocked by a creature, that creature gets -1/-1 until end of turn.

Whenever Order of the Golden Cricket attacks, you may pay . If you do, it gains flying until end of turn.

Defender (This creature can't attack.)

As Order of the Stars enters, choose a color.

Order of the Stars has protection from the chosen color.