msem-instigator

Equipped creature gets +0/+3 and has menace. (It can't be blocked except by two or more creatures.)
Equip {1}

Ominous Lair enters tapped unless you have 15 or less life.
{T}: Add {W} or {B}.

{T}: Add {U} or {B}. You lose 1 life unless you have less life than an opponent.

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

Onoran Runeglyphs enters tapped.
{T}: Add two mana in any combination of colors from among creatures you control.
Menagerie — {2}, {T}: Draw a card. Activate only if there are five or more creature types among creatures you control.

Opalescent Heirloom enters with a charge counter on it for each color of mana spent to cast it.
Equipped creature gets +1/+1 for each charge counter on Opalescent Heirloom.
Equip—{3} or remove a charge counter from Opalescent Heirloom.

{T}: Add {U} or {R}. You lose 1 life unless you have less life than an opponent.

Search your library for a land card, reveal it, then shuffle and put that card on top. (Then exile this card. You may play the land later from exile.)

At the beginning of your upkeep, each player conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

Opera House enters tapped.
When Opera House enters, add one mana of any color.
{T}, Sacrifice Opera House: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Whenever another nonland permanent you control enters, return that permanent to its owner's hand at the beginning of the next end step.

Equipped creature gets +1/+1.
Whenever equipped creature deals combat damage to a player, Ornamental Longbow deals 1 damage to any target.
Equip {2}

Ornamented Evergreen enters tapped unless you have two or more opponents.
{T}: Add {G} or {W}.

{1}, Sacrifice Ornate Incense: Draw a card. You gain 1 life.

You may cast spells as though they had flash.

({T}: Add {G}.)
Wanderlust — Otherworldly Forest enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

({T}: Add {U}.)
Wanderlust — Otherworldly Island enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

({T}: Add {R}.)
Wanderlust — Otherworldly Mountain enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

({T}: Add {W}.)
Wanderlust — Otherworldly Plains enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

({T}: Add {B}.)
Wanderlust — Otherworldly Swamp enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

When Over the Horizon enters, scry 1.
{T}: Add {C}.
{1}, {T}: Return Over the Horizon to its owner's hand.

Overgrown Enclave enters tapped.
{T}: Add {G} or {U}.
{4}{G}{U}: Until end of turn, Overgrown Enclave becomes a Turtle creature with ward {2} in addition to its other types.
Scavenge {5}{G}{U}

{T}, Pay 1 life: Add {G} or {W}.
{1}, {T}, Sacrifice Overgrown Refuge: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Overgrown Ruins enters tapped.
As Overgrown Ruins enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

{T}: Add {C}.
{7}, {T}: Copy target instant or sorcery spell with {X} in its mana cost. You may choose new targets for the copy. This ability costs {1} less to activate for each instant and sorcery card in your graveyard.