Ina Wong

"Oh, I can absolutely verify its authenticity," chuckled Sarnai. "I was there when it was made."

Sibsig Appraiser

When this creature enters, look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.

Markov Baron

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Lifelink
Other Vampires you control get +1/+1.
Madness {2}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Argothian Opportunist

When this creature enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Roxanne, Starfall Savant

Whenever Roxanne, Starfall Savant enters the battlefield or attacks, create a tapped colorless artifact token named Meteorite with "When Meteorite enters the battlefield, it deals 2 damage to any target" and "{T}: Add one mana of any color."
Whenever you tap an artifact token for mana, add one mana of any type that artifact token produced.

Whenever Roxanne enters or attacks, create a tapped colorless artifact token named Meteorite with "When this token enters, it deals 2 damage to any target" and "{T}: Add one mana of any color."
Whenever you tap an artifact token for mana, add one mana of any type that artifact token produced.

Rakish Scoundrel

Deathtouch
When Rakish Scoundrel enters the battlefield or is turned face up, target creature gains indestructible until end of turn.
Disguise {4}{BG}{BG} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)

Deathtouch
When this creature enters or is turned face up, target creature gains indestructible until end of turn.
Disguise {4}{B/G}{B/G} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)

"Of course! It was all so obvious. I should have made the connection days ago."
—Alquist Proft, case notes

Deduce

Draw a card. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

"Never track the roc itself with your eyes, for it will swoop with the sun at its back and blind you. Instead, track its shadow and, when it's almost upon you, heave your javelin upward with all your might."

Roc Hunter

Meteorite

When Meteorite enters the battlefield, it deals 2 damage to any target.
{T}: Add one mana of any color.

Party Thrasher

Noncreature spells you cast from exile have convoke.
At the beginning of your precombat main phase, you may discard a card. If you do, exile the top two cards of your library, then choose one of them. You may play that card this turn.

Noncreature spells you cast from exile have convoke. (Each creature you tap while casting a noncreature spell from exile pays for {1} or one mana of that creature's color.)
At the beginning of your first main phase, you may discard a card. If you do, exile the top two cards of your library, then choose one of them. You may play that card this turn.