msem-instigator

Instant and sorcery spells you cast cost {1} less and an additional 1 life to cast.
You control your opponents while instant and sorcery spells you control are resolving.

{R}{W}{B}, Discard a card named Ni'Ama, God of Adversity: Ni'Ama gains indestructible and becomes a God creature in addition to its other types.
Whenever Ni'Ama enters or attacks, it deals 2 damage to each opponent unless they discard a card. You gain that much life. Repeat this process once.

Whenever a storied permanent you control enters, each opponent discards a card. (Enchantments and legendary permanents are storied.)

Indestructible
When this creature transforms into Ninhasir, God of Creation, discard all the cards in your hand, then draw that many cards plus one.
Whenever you cast an instant or sorcery spell, copy it. You may choose new targets for the copy.

When Norwick Militia enters, other Citizens and Peasants you control get +1/+1 and gain vigilance until end of turn.

Trample
When Oakcudgel Giant enters, you may destroy target artifact or enchantment.

Trample
Assault {1}{G} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Whenever a creature you control with a +1/+1 counter on it deals combat damage to a player, draw a card.

Flash
Ocean's Edge Kraken enters with a hexproof counter on it.
{6}{U}{U}, Remove a hexproof counter from Ocean's Edge Kraken: Return all other creatures to their owners' hands.

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.)

Defender, flying
Menagerie — As long as there are five or more creature types among creatures you control, Old-Rune Sentinel can attack as though it didn't have defender.

Trample, haste
Whenever an opponent casts a noncreature spell, you may return Olten Sandwurm to its owner's hand.

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.

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.

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.

Flying
Creatures you don't control have “{T}: This creature fights Ontarachie Apex. Activate only as a sorcery.”

Trample
Whenever Openmaw Demon or another Azra or Demon you control enters, you may exile target card from a graveyard.

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.

All creatures able to block Orphaned Nuckalavee do so.

Flying, vigilance
Orzhov Benefactor can't attack or block unless you pay {1} for each debt counter on it.
At the beginning of your upkeep, put a debt counter on Orzhov Benefactor.
{2}: Remove a debt counter from Orzhov Benefactor.

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.

When this creature enters, target creature seeks secrets. (Give it that Oath Aura. Fulfill it by attacking with it and two or more other creatures to draw a card.)
Whenever you draw a card, each opponent loses 1 life and you gain 1 life.

Flying

Reach
Whenever Palm Walker or another creature you control enters, you gain 2 life.

Flying
Other creatures get -1/-1.
Whenever Pan Long enters or deals combat damage to a player, return to the battlefield under your control target creature card from a graveyard that was put there from the battlefield this turn.

Menace
Landfall — Whenever a land you control enters, create two 1/1 red and white Warrior creature tokens with haste. Exile them at the beginning of the next end step.