Forensic Gadgeteer

Whenever you cast an artifact spell, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Activated abilities of artifacts you control cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Tenth District Hero

{1}{W}, Collect evidence 2: Tenth District Hero becomes a Human Detective with base power and toughness 4/4 and gains vigilance.
{2}{W}, Collect evidence 4: If Tenth District Hero is a Detective, it becomes a legendary creature named Mileva, the Stalwart, it has base power and toughness 5/5, and it gains "Other creatures you control have indestructible."

Search the Premises

Whenever a creature attacks you or a planeswalker you control, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Wojek Investigator

Flying, vigilance
At the beginning of your upkeep, investigate once for each opponent who has more cards in hand than you. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Piper Wright, Publick Reporter

Whenever Piper Wright deals combat damage to a player, investigate that many times. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you sacrifice a Clue, put a +1/+1 counter on target creature you control.

Inspiring Statuary

Nonartifact spells you cast have improvise. (Your artifacts can help cast those spells. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Martha Jones

Woman Who Walked the Earth — When Martha Jones enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you sacrifice a Clue, Martha Jones and up to one other target creature can't be blocked this turn.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Case of the Pilfered Proof

Whenever a Detective you control enters or is turned face up, put a +1/+1 counter on it.
To solve — You control three or more Detectives. (If unsolved, solve at the beginning of your end step.)
Solved — If one or more tokens would be created under your control, those tokens plus a Clue token are created instead. (It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

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.

Burden of Proof

Flash
Enchant creature
Enchanted creature gets +2/+2 as long as it's a Detective you control. Otherwise, it has base power and toughness 1/1 and can't block Detectives.

Sally Sparrow

You may cast creature spells as though they had flash.
Whenever one or more other creatures you control leave the battlefield, investigate. This ability triggers only once each turn. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Tangletrove Kelp

Ward {2}
At the beginning of each combat, other Clues you control become 6/6 Plant creatures in addition to their other types until end of turn.
{2}, Sacrifice Tangletrove Kelp: Draw a card.

Reenact the Crime

Exile target nonland card in a graveyard that was put there from anywhere this turn. Copy it. You may cast the copy without paying its mana cost.

Thinking Cap

Equipped creature gets +1/+2.
Equip Detective {1}
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Deduce

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

Armed with Proof

When Armed with Proof enters, investigate twice. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Clues you control are Equipment in addition to their other types and have "Equipped creature gets +2/+0" and equip {2}.

Officious Interrogation

This spell costs {W}{U} more to cast for each target beyond the first.
Choose any number of target players. Investigate X times, where X is the total number of creatures those players control.

Junk Winder

Affinity for tokens (This spell costs {1} less to cast for each token you control.)
Whenever a token you control enters, tap target nonland permanent an opponent controls. It doesn't untap during its controller's next untap step.

Ethereal Investigator

Flying
When Ethereal Investigator enters, investigate X times, where X is the number of opponents you have. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you draw your second card each turn, create a 1/1 white Spirit creature token with flying.

Novice Inspector

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

No More Lies

Counter target spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Perimeter Enforcer

Flying, lifelink
Whenever another Detective you control enters and whenever a Detective you control is turned face up, Perimeter Enforcer gets +1/+1 until end of turn.

Merchant of Truth

Flying
Whenever a nontoken creature you control dies, investigate.
Clues you control have exalted. (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn for each instance of exalted among permanents you control.)

Alquist Proft, Master Sleuth

Vigilance
When Alquist Proft, Master Sleuth enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
{X}{W}{U}{U}, {T}, Sacrifice a Clue: You draw X cards and gain X life.

Erdwal Illuminator

Flying
Whenever you investigate for the first time each turn, investigate an additional time.

Magnifying Glass

{T}: Add {C}.
{4}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Reasonable Doubt

Counter target spell unless its controller pays {2}.
Suspect up to one target creature. (A suspected creature has menace and can't block.)

Ezrim, Agency Chief

Flying
When Ezrim, Agency Chief enters, investigate twice. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
{1}, Sacrifice an artifact: Ezrim gains your choice of vigilance, lifelink, or hexproof until end of turn.

Kappa Cannoneer

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Ward {4}
Whenever Kappa Cannoneer or another artifact you control enters, put a +1/+1 counter on Kappa Cannoneer and it can't be blocked this turn.

Time Wipe

Return a creature you control to its owner's hand, then destroy all creatures.

Private Eye

Other Detectives you control get +1/+1.
Whenever you draw your second card each turn, target Detective can't be blocked this turn.

Hydroelectric Laboratory

As Hydroelectric Laboratory enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {U}.

Hydroelectric Specimen

Flash
When Hydroelectric Specimen enters, you may change the target of target instant or sorcery spell with a single target to Hydroelectric Specimen.

Hydroelectric Specimen // Hydroelectric Laboratory

Disorder in the Court

Exile X target creatures, then investigate X times. Return the exiled cards to the battlefield tapped under their owners' control at the beginning of the next end step. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Detective of the Month

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
As long as you have the city's blessing, Detectives you control can't be blocked.
Whenever you draw your second card each turn, create a 2/2 white and blue Detective creature token.

Projektor Inspector

Whenever Projektor Inspector or another Detective you control enters and whenever a Detective you control is turned face up, you may draw a card. If you do, discard a card.

Mistway Spy

Flying
Disguise {1}{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 Mistway Spy is turned face up, until end of turn, whenever a creature you control deals combat damage to a player, investigate.