Flying, first strike, lifelink
Landfall — Whenever a land you control enters, other creatures you control get +2/+2 until end of turn.

First strike
Landfall — Whenever a land you control enters, other creatures you control get +1/+1 until end of turn.
{2}{R}{W}{B}: Transform Omenhorn.

Ominous Quag enters tapped.
{T}: Add {W} or {B}.
{2}{W}{B}, {T}, Sacrifice Ominous Quag: Draw a card.

Your maximum hand size is zero.
Pay 1 life: Draw a card. Activate only as a sorcery.

Whenever Omnoid Destroyer or another artifact you control enters, artifact creatures you control gain deathtouch until end of turn.

Create three 1/1 red and green Elemental creature tokens.

Whenever Opal-Eye Allseer enters or you cast a noncreature spell, create a 1/1 white Bird creature token with flying.
Wander—{1}{U}, Exile two instant and/or sorcery cards from your graveyard.

Whenever a nontoken creature you control enters, if it wasn't cast from your hand, put a +1/+1 counter on that creature.
Wander {2}{W}

Flying, haste
As an additional cost to cast spells with flashback, you may pay {1}{R}. When you do, return Opal-Eye Phoenix from your graveyard to the battlefield.

Whenever you spend at least five mana to cast a spell, untap Opal-Eye Runeweaver.
{T}: Untap another target permanent not named Opal-Eye Runeweaver. Activate only as a sorcery.

Open Air Boardwalk enters tapped.
{T}: Add {G} or {W}.
{4}: Make a pledge. Activate only as a sorcery.

When Opulent Roughrider enters or leaves the battlefield, surveil 1, then you may reveal the top card of your library. If that card has the same name as a permanent you control or a card in your graveyard, put it into your hand.
Wander {4}{U}{U}

Vigilance
Whenever you attack, bless target creature.

Whenever you cast an instant or sorcery spell, untap Orbinoid.
{T}: Add one mana of any type.

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 Athreos.
When you sacrifice Ordeal of Athreos, return target creature card from your graveyard to the battlefield.

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 Ephara.
When you sacrifice Ordeal of Ephara, return up to two target nonland permanents to their owner's hand.

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 Karametra.
Whenever you sacrifice Ordeal of Karametra, put a +1/+1 counter on each creature you control. Untap them.

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 Karda.
Whenever you sacrifice Ordeal of Karda, creatures you control get +2/+0 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 Pharika.
Whenever you sacrifice Ordeal of Pharika, creatures your opponents control get -2/-2 until end of turn.

Creatures you control have menace as long as they are attacking players with eight or more cards in their graveyard.
Whenever you attack, each defending player mills two cards. If a land card was milled this way, put a +1/+1 counter on Orestes.

Until end of turn, target creature you control gets +2/+2 and gains “Whenever this creature is dealt damage, you may have it fight target creature you don't control.” Then, it fights target creature you don't control.

Target creature you control gains hexproof until end of turn. When a nonmana ability of that creature is next activated or triggered this turn, copy it. You may choose new targets for the copy.

Exile target creature or planeswalker. Its controller loses 2 life.

Outlands Prowler has first strike as long as it's your turn.
Landfall — Whenever a land you control enters, Outlands Prowler gets +2/+2 until end of turn.

Counter target spell. That spell's controller reveals their hand. Choose any number of nonland cards from it. That player puts those cards on the bottom of their library in any order, then draws that many cards.