Whenever an enchantment you control enters, each opponent mills two cards.

Whenever an enchantment you control enters, tap target noncreature permanent.

During your turn, you may play cards from your graveyard but not from anywhere else.
Whenever you cast an instant or sorcery spell, exile that card instead of putting it into your graveyard as it resolves.
If another permanent you control would be put into your graveyard, exile it instead.

Reach, deathtouch
Once each turn, when a counter is put on a creature you control, you may put a counter of that kind on another creature you control.

Flash
When Omen of Deception enters, counter target spell unless its controller pays {2}.
{2}{U}, Sacrifice Omen of Deception: Scry 2.

Flash
When Omen of Horizons enters, put two +1/+1 counters on target creature you control.
{2}{G}, Sacrifice Omen of Horizons: Scry 2.

Flash
When Omen of Slaughter enters, each opponent sacrifices a creature or planeswalker.
{2}{B}, Sacrifice Omen of Slaughter: Scry 2.

Flash
When Omen of Storms enters, discard a card, then draw two cards.
{2}{R}, Sacrifice Omen of Storms: Scry 2.

Flash
When Omen of Victory enters, create a 0/0 white Army creature token, then put two +1/+1 counters on it.
{2}{W}, Sacrifice Omen of Victory: Scry 2.

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.

Put a vigilance counter on target creature you control. That creature deals damage equal to its power to up to one target creature you don't control.

Enchant creature you control
At the beginning of each combat, other creatures you control gain first strike until end of turn if enchanted creature has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, trample, vigilance, and ward.

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
When Ordained Penitence enters, you may put a lifelink counter on target creature you control.
Enchanted creature can't attack or block, and its activated abilities can't be activated.

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.