Unyielding Gatekeeper

Disguise {1}{W} (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.)
When Unyielding Gatekeeper is turned face up, exile another target nonland permanent. If you controlled it, return it to the battlefield tapped. Otherwise, its controller creates a 2/2 white and blue Detective creature token.

Swamp

Granite Witness

Flying, vigilance
Disguise {W/U}{W/U} (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.)
When Granite Witness is turned face up, you may tap or untap target creature.

Novice Inspector

When Novice Inspector enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Innocent Bystander

Whenever Innocent Bystander is dealt 3 or more damage, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Tomik, Wielder of Law

Affinity for planeswalkers (This spell costs {1} less to cast for each planeswalker you control.)
Flying, vigilance
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, that opponent loses 3 life and you draw a card.

Seasoned Consultant

Whenever you attack with three or more creatures, Seasoned Consultant gets +2/+0 until end of turn.

Dog Walker

Vigilance
Disguise {R/W}{R/W} (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.)
When Dog Walker is turned face up, create two tapped 1/1 white Dog creature tokens.

Escape Tunnel

{T}, Sacrifice Escape Tunnel: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{T}, Sacrifice Escape Tunnel: Target creature with power 2 or less can't be blocked this turn.

Meddling Youths

Haste
Whenever you attack with three or more creatures, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Person of Interest

When Person of Interest enters, suspect it. Create a 2/2 white and blue Detective creature token. (A suspected creature has menace and can't block.)

Fugitive Codebreaker

Prowess, haste
Disguise {5}{R}. This cost is reduced by {1} for each instant and sorcery card in your graveyard. (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.)
When Fugitive Codebreaker is turned face up, discard your hand, then draw three cards.

Aurelia, the Law Above

Flying, vigilance, haste
Whenever a player attacks with three or more creatures, you draw a card.
Whenever a player attacks with five or more creatures, Aurelia, the Law Above deals 3 damage to each of your opponents and you gain 3 life.

Suspicious Detonation

This spell costs {3} less to cast if you've sacrificed an artifact this turn.
This spell can't be countered. (This includes by the ward ability.)
Suspicious Detonation deals 4 damage to target creature.

Museum Nightwatch

When Museum Nightwatch dies, create a 2/2 white and blue Detective creature token.
Disguise {1}{W} (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.)

Plains

Goblin Maskmaker

Whenever Goblin Maskmaker attacks, face-down spells you cast this turn cost {1} less to cast.

Marketwatch Phantom

Whenever another creature you control with power 2 or less enters, Marketwatch Phantom gains flying until end of turn.

Makeshift Binding

When Makeshift Binding enters, exile target creature an opponent controls until Makeshift Binding leaves the battlefield. You gain 2 life.

Call a Surprise Witness

Return target creature card with mana value 3 or less from your graveyard to the battlefield. Put a flying counter on it. It's a Spirit in addition to its other types.

Wrench

Equipped creature gets +1/+1 and has vigilance and "{3}, {T}: Tap target creature."
{2}, Sacrifice Wrench: Draw a card.
Equip {2}

Vengeful Tracker

Whenever an opponent sacrifices an artifact, Vengeful Tracker deals 2 damage to them.

Torch the Witness

Torch the Witness deals twice X damage to target creature. If excess damage was dealt to that creature this way, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")