mtg.wtf

Flying
When Oltec Cloud Guard enters the battlefield, create a 1/1 colorless Gnome artifact creature token.

Flash
When Omen of the Dead enters the battlefield, return target creature card from your graveyard to your hand.
{2}{B}, Sacrifice Omen of the Dead: Scry 2.

Flash
When Omen of the Forge enters the battlefield, it deals 2 damage to any target.
{2}{R}, Sacrifice Omen of the Forge: Scry 2.

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.
{2}{G}, Sacrifice Omen of the Hunt: Scry 2.

Flash
When Omen of the Sea enters the battlefield, scry 2, then draw a card.
{2}{U}, Sacrifice Omen of the Sea: Scry 2.

Flash
When Omen of the Sun enters the battlefield, create two 1/1 white Human Soldier creature tokens and you gain 2 life.
{2}{W}, Sacrifice Omen of the Sun: Scry 2.

When Omenpath Journey enters the battlefield, search your library for up to five land cards that have different names, exile them, then shuffle.
At the beginning of your end step, choose a card at random exiled with Omenpath Journey and put it onto the battlefield tapped.

When Omenspeaker enters the battlefield, scry 2.

When Ominous Roost enters the battlefield or 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."

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 the battlefield, draw a card.
Landfall — Whenever a land enters the battlefield under your control, you gain 4 life if this is the first time this ability has resolved this turn. If it's the second time, add {R}{G}{W}{U}. If it's the third time, Omnath deals 4 damage to each opponent and each planeswalker you don't control.

When Omnath, Locus of the Roil enters the battlefield, it deals damage to any target equal to the number of Elementals you control.
Landfall — Whenever a land enters the battlefield under your control, put a +1/+1 counter on target Elemental you control. If you control eight or more lands, draw a card.

Enchant snow land you control
When On Thin Ice enters the battlefield, exile target creature an opponent controls until On Thin Ice leaves the battlefield.

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

When Opal Lake Gatekeepers enters the battlefield, if you control two or more Gates, you may draw a card.

Flying
When Opportunistic Dragon enters the battlefield, choose target Human or artifact an opponent controls. For as long as Opportunistic Dragon remains on the battlefield, gain control of that permanent, it loses all abilities, and it can't attack or block.

Haste
Tribute 2
When Oracle of Bones enters the battlefield, if tribute wasn't paid, you may cast an instant or sorcery spell from your hand without paying its mana cost.

When Oracle of Tragedy enters the battlefield or dies, choose one —
• Draw a card, then discard a card.
• Shuffle up to four target cards with mana value 3 or greater from your graveyard into 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.

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.

Kicker {2}{G}
Reach
When Oran-Rief Recluse enters the battlefield, if it was kicked, destroy target creature with flying.

As an additional cost to cast this spell, you may reveal a Dragon card from your hand.
Defender, flying
When Orator of Ojutai enters the battlefield, if you revealed a Dragon card or controlled a Dragon as you cast this spell, draw a card.

Council's dilemma — When Orchard Elemental enters the battlefield, starting with you, each player votes for sprout or harvest. Put two +1/+1 counters on Orchard Elemental for each sprout vote. You gain 3 life for each harvest vote.

When Orchard Strider enters the battlefield, create two Food tokens.
Basic landcycling {1}{G}

Flash
When Orcish Bowmasters enters the battlefield and whenever an opponent draws a card except the first one they draw in each of their draw steps, Orcish Bowmasters deals 1 damage to any target. Then amass Orcs 1.