msem-instigator

Reach
When Oaken Sentry enters, you gain 1 life for each creature card in your graveyard.

Defender, first strike
{1}{G}: Oaken Spearman can attack this turn as though it didn't have defender.

Search your library for two basic land cards, reveal them, put them into your hand, then shuffle.

Whenever you cast a cryptic spell, Oasis Cattle gets +1/+1 until end of turn, then untap it. (Artifacts, enchantments, and modal spells are cryptic.)

Defender
As long as your fealty to Islands is six or greater, Oasis Glutton can attack as though it didn't have defender. (Each Island you control counts towards your fealty to Islands.)

Search your library for a basic land card or Desert card, reveal it, put it into your hand, then shuffle.
Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Vigilance
When this creature dies, target creature you control seeks secrets or valor. (Give it that Oath Aura. Fulfill secrets by attacking with it and two or more other creatures to draw a card. Fulfill valor by dealing combat damage to a player to create a 2/1 white Soldier token.)

When Oathkeeper's Verdict enters, tap all creatures your opponents control.
Equipped creature gets +3/+3.
Equip {3}

Lifelink
When this creature enters, it seeks secrets. (Give it that Oath Aura. Fulfill it by attacking with it and two or more other creatures to draw a card.)

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.

Target opponent exiles a card from their hand. Scry 2.
Tether (Then if you cast this from your hand, you may exile it tethered to a creature you control. When it dies, you may cast this from exile without paying its mana cost.)

When Obscure Apostle enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Whenever you sacrifice an Idol, Obscure Apostle can't be blocked this turn.

Return target creature to its owner's hand.
Concord — If there are four or more card types among permanents you control, draw a card.

Observation Field enters with three charge counters on it.
{2}, {T}, Remove a charge counter from Observation Field: Draw a card and gain 2 life.
{T}, Sacrifice Observation Field: Shuffle any number of target cards from your graveyard into your library.

Tribute 2 (As this creature enters, an opponent of your choice may put two +1/+1 counters on it.)
When Observing Guardian enters, if tribute wasn't paid, create a 2/2 white Cat creature token.

Flying
When Obsidian Hellkite dies, it deals 2 damage to up to one target creature or planeswalker. If that creature or planeswalker would die this turn, exile it instead.
Foreshadow {4}{R}{R} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

Put target nonland permanent on top of its owner's library. Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

When Occult Mastermind enters, create two 2/2 black Zombie creature tokens. When Occult Mastermind is no longer on the battlefield, sacrifice two Zombies.

Attacking creatures get -2/-0 until end of turn.
Metamorph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up and cast it at any time for its metamorph cost.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
{T}: Salvage a creature card. (Exile one 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.)

Whenever one or more artifacts you control enter, put a +1/+1 counter on Octopus Shiny-Grabber and you gain 1 life.

Flash
When Odaya Magistrate enters, you may counter target noncreature spell.

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.)

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.

You may pay {R} and tap an untapped Warrior you control rather than pay this spell's mana cost.
Choose one —
• Double the power of target creature you control until end of turn.
• Target creature you control deals damage equal to its power to target creature or planeswalker.