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.)

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.

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

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.

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.”)

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.)

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

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.

Destroy target artifact or enchantment. Scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

As an additional cost to cast this spell, sacrifice a permanent.
Draw two cards.

{2}, {T}, Sacrifice Old Map: Search your library for a basic land card, put it onto the battlefield, then shuffle.

When Old Salt enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

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.

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.

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

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.

Haste (This creature can attack and {T} as soon as it comes under your control.)
Olson's Sky Brigade has flying as long as you control another attacking Pirate.