msem-instigator

Nizev Temple enters tapped.
Satrapies you control have “{T}: Add {U} or {B}.”

Put target permanent card with mana value 3 or less from a graveyard onto the battlefield under your control.
Leitmotif (If you cast this spell from your hand, exile it as it resolves. When you next cast a spell that shares a color with this card, you may cast this from exile without paying its mana cost.)

({T}: Add {B} or {G}.)
Whenever Nomad's Township becomes tapped, you lose 1 life unless you control two or more basic lands.

When Nomadic Patriarch enters, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)
Remove a +1/+1 counter from Nomadic Patriarch: Put a +1/+1 counter on each other creature token you control.

You may return a land you control to its owner's hand rather than pay this spell's mana cost.
Northern Express Line enters tapped.
{T}: Add {U}.

Primal {5}{G}{U} (During your turn, you may cast this spell for {5}{G}{U} instead of playing a land.)
If you cast this spell for its primal cost, search your library for a permanent card, reveal it, put it into your hand, then shuffle.
You may put a permanent card from your hand onto the battlefield.

Enchant player
At the beginning of enchanted player's end step, gain control of a permanent they control.

Flying
When Novaheart Guardian enters, it deals 4 damage to any target.
Whenever a creature or planeswalker dies, put a +1/+1 counter on Novaheart Guardian.

Reverberate—Sacrifice a Swamp. (When you cast this spell, copy it if you paid its reverberate cost.)
All creatures get -2/-2 until end of turn.

Trample
Whenever you attack with another creature with power 4 or greater, put a +1/+1 counter on OH-14 Diamond.

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.

Oathbreaker Orc attacks each combat if able.
Whenever Oathbreaker Orc attacks, it deals 2 damage to defending player unless that player sacrifices a permanent.

Obliterating Blast deals 3 damage to any target. A creature dealt damage this way this turn can't be regenerated this turn. If that creature would die this turn, exile it instead.

Obscoriate deals 4 damage to target creature or planeswalker. The next time that permanent would die this turn, instead put a basalt counter on it, it becomes a Mountain land named Charred Remains, loses all other card types, and gains “At the beginning of your upkeep, Charred Remains deals 1 damage to you.” (It has “{T}: Add {R}” and loses abilities it already had.)

This spell costs {1} less to cast for each artifact and/or enchantment you control.
Trample
{1}, Sacrifice another cryptic permanent you control or exile a cryptic card from your graveyard: Put a +1/+1 counter on Observer of Aeons. (Artifacts, enchantments, and modal spells are cryptic.)

Whenever you attack, you may double target attacking creature's power. If you do, sacrifice it at the beginning of the next step.
Whenever one or more red creatures you control enter, creatures you control get +1/+0 and gain trample until end of turn.

As Ocean Monastery enters, you may pay 2 life. If you don't, Ocean Monastery enters tapped.
{T}, Sacrifice Ocean Monastery: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

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.

Exile up to two target creatures controlled by different players. Return those creatures to the battlefield under their owners' control at the beginning of the next end step.

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

Trample, haste
When Oil Driller enters, salvage two cards at random. (Exile those cards from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)
At the beginning of your end step, sacrifice Oil Driller.

Other Merfolk you control get +1/+1.
When Olantin Pearlreader enters, scry 2. Then draw a card if you control two or more other Merfolk.

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

Oldgrove Nurturer enters with a +1/+1 counter on it.
{G}, Remove a +1/+1 counter from a creature you control: Create a 1/1 colorless Construct artifact creature token.

Whenever you attack with one or more Pirates, create that many 1/1 white Bird creature tokens with flying that are tapped and attacking. At end of combat, choose one of those tokens, then exile the rest.