msem-instigator

Search your library for a nongreen creature card with mana value X or less and put that card onto the battlefield, then shuffle. That creature 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.)

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.)

At the beginning of your end step, judge target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Target opponent takes an extra turn after this one. Until your next turn, you control that player during extra turns.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

{T}: Put a luster counter on Object of Awe.
{1}{R}, {T}: Discard up to X cards, then draw a card for each card discarded this way. X is the number of luster counters on Object of Awe.
{3}{R}: Until end of turn, Object of Awe becomes an X/X red Phoenix creature with flying, where X is the number of luster counters on Object of Awe.

Whenever a creature enters, destroy it unless its controller pays 3 life.

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.

Flash
Whenever you cast an artifact or enchantment spell, put a +1/+1 counter on Observer of Secret Paths. It can't be blocked this turn.

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.

Other creatures you control get +2/+0.
Creatures your opponents control get -1/-1.
Fleeting {2}{B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

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.)

Flying
Whenever you cast a noncreature spell, you may exchange control of it and target creature. Then the spell's controller may choose new targets for it.

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.

At the beginning of your end step, create a token that's a copy of target transformed permanent you control, except it has “This permanent can't transform.”

Tithe (As you cast this spell, you may tap three artifacts and/or creatures you control.)
Search your library for a card and put that card into your hand, then shuffle. If this spell's tithe was paid, add {B}{B}{B}{B}.

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.)

Motley — At the beginning of combat on your turn, if there are five or more names among nonland permanents you control, Ochre Knight gets +2/+1 until end of turn and you gain 1 life.

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