msem-instigator

Motley — At the beginning of combat on your turn, if there are five or more names among nonland permanents you control, Ochre Knight gets +2/+1 until end of turn and you gain 1 life.

Ode to the Red Wind deals 1 damage to target creature. It can't block this turn.
Showcase {3}{R} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Each player sacrifices a creature. If a player lost 3 or more life this turn, each opponent sacrifices a creature instead.

{T}: You may put a land card from your hand onto the battlefield.
{1}, {T}: Aetherize target land you control. (To aetherize, create a token that's a copy of it, then exile that token.)

Enchant planeswalker
Enchanted planeswalker has “+2: Draw two cards, then put a card from your hand on the bottom of your library.”

Target creature gets -X/-X until end of turn, where X is the number of enchantments you control.

When Old-Oath Conviction enters or leaves the battlefield, create a 1/1 white Cleric creature token with lifelink.
{3}{B}, Sacrifice Old-Oath Conviction: Draw a card. Activate only as a sorcery.

{T}: Add {C}.
{6}, {T}, Discard a card: Search your library for a multicolored card, exile it, then shuffle. If its mana value is 3 or less, you may cast it without paying its mana cost. If you don't, put it into your hand. Activate only as a sorcery.

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.

Return target creature card with mana value 3 or less from your graveyard to the battlefield. If its mana value is less than 3, you gain life equal to the difference.

Target creature you control gains haste until end of turn. Return it to its owner's hand at the beginning of the next end step.

Enchant creature
Whenever enchanted creature deals combat damage to a player, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. Scry 2.

Whenever Ontarachie Hunter attacks, each opponent loses 1 life.
At the beginning of your end step, if an opponent has 10 or less life, transform Ontarachie Hunter.

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.

Whenever Open Road or another permanent you control enters, if it has the greatest mana value among permanents you control, you may discard a card. If you do, 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.

{T}: Add {G}. If you control an attacking creature, add one mana of any color instead.

Enchant creature
Enchanted creature can't attack or block unless its controller pays {3}.
Activated abilities of enchanted creature cost {3} more to activate.

Scry 1.
Draw a card.

When Oracle Crab enters, scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Search your library for up to six cards and exile them face down. Shuffle, then draw a card.