msem-instigator

When Okus, the Fabulous Hat enters, gain control of target creature or planeswalker for as long as you control Okus.
[+1]: You may create a blue Aura enchantment token named Fancy Hat with enchant creature and “Enchanted creature gets -2/-0.”
[–2]: Target player loses life equal to the number of enchantments you control and you gain that much life.

When Ol' Sycamore enters, choose up to two —
• Ol' Sycamore fights another target legendary creature.
• Destroy target noncreature storied permanent. (Enchantments and legendary permanents are storied.)

Flying
Menagerie — When Old-Rune Watcher enters, if there are five or more creature types among creatures you control, draw a card.

Flying
When Old-World Forgotten dies, you may return target artifact or enchantment card from your graveyard to your hand.

Flash
Flying

Reach
When Oltenen Terror enters, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
{1}{G}, Sacrifice an artifact or creature: Tap Oltenen Terror. It gains indestructible until end of turn.

Whenever you cast a noncreature spell, Omegalomania deals 2 damage to any target. Whenever a permanent you don't control dealt damage this way dies this turn, return it to the battlefield tapped under your control.

Play with the top card of your library revealed.
Whenever you draw a card, destroy each creature with the same mana value as that card.

When Ominous Presence enters, search your library for a Curse card, reveal it, then shuffle. If it has mana value 4 or less, you may put it onto the battlefield. Otherwise, put it into your hand.
Ominous Presence gets +1/+1 for each Curse attached to your opponents.

This spell costs {1}{U} less to cast if it targets a red or green spell.
Counter target spell.
Draw a card.

For each player, choose a creature or planeswalker that player controls. Each player sacrifices all creatures and planeswalkers they control not chosen this way.
Fuse (You may cast one or both halves of this card from your hand.)

Return target creature card from your graveyard to the battlefield. Then up to one target opponent sacrifices a creature if you control an Angel, Demon, Faerie, or Spirit.

Spells your opponents cast that target Onigori, Ema's Shield cost {2} more to cast.
Whenever Onigori deals combat damage to a player, that player can't untap more than two permanents during their next untap step.

Return target creature card from your graveyard to the battlefield, then rediscover a creature card. (Look at the top card of your library. You may reveal it and put it into your hand if it's a creature card. Otherwise, put it back or into your graveyard.)

When Ophidian Oracle enters, draw a card, then abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
Recite {2}{G}{G} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Creatures can't attack you unless their controller pays {3} for each of those creatures.

Target creature gets -5/-5 until end of turn.
Judge up to one target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Whenever Ore Tunneler deals damage to an opponent, tap target land they control. It doesn't untap during its controller's next untap step.

Flying, deathtouch
Once each turn, when you cast a spell from your graveyard, you may cast target card in your graveyard with lesser mana value than that spell without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Whenever Orria Mirrorpelt becomes the target of a spell, exile that spell. If Orria Mirrorpelt was its only target, copy it for each other creature target player controls. Each copy targets a different one of those creatures.

Primal {1}{G}{G} (During your turn, you may cast this spell for {1}{G}{G} instead of playing a land.)
When Orria's Ward enters, if you played a land this turn, draw a card. Otherwise, put two +1/+1 counters on it.

Lifelink
At the beginning of your upkeep, Osgaerith Desecrator deals 1 damage to up to one target creature.

All creatures able to block Osheen Courtier do so.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Deception {2}{U} ({2}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
When Oshiruko Silencer enters, return target creature to its owner's hand.

Trample
Whenever Oshu deals combat damage to a player, gain control of target land that player controls. It becomes a 4/4 Elemental creature that's still a land.
As long as you control eight or more lands, Oshu and land creatures you control get +2/+2.