The Chase Is On

Target creature gets +3/+0 and gains first strike until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Crime Novelist

Whenever you sacrifice an artifact, put a +1/+1 counter on this creature and add {R}.

Shock

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 this creature is turned face up, discard your hand, then draw three cards.

Lamplight Phoenix

Flying
When this creature dies, you may exile it and collect evidence 4. If you do, return this card to the battlefield tapped. (To collect evidence 4, exile cards with total mana value 4 or greater from your graveyard.)

Vengeful Tracker

Whenever an opponent sacrifices an artifact, this creature deals 2 damage to them.

Frantic Scapegoat

Haste
When this creature enters, suspect it. (It has menace and can't block.)
Whenever one or more other creatures you control enter, if this creature is suspected, you may suspect one of the other creatures. If you do, this creature is no longer suspected.

Red Herring

Haste
This creature attacks each combat if able.
{2}, Sacrifice this creature: Draw a card.

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 token: Draw a card.")

Mountain

Knife

During your turn, equipped creature gets +1/+0 and has first strike.
{2}, Sacrifice this Equipment: Draw a card.
Equip {2}

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.

Demand Answers

As an additional cost to cast this spell, sacrifice an artifact or discard a card.
Draw two cards.

Krenko, Baron of Tin Street

Haste
{T}, Sacrifice an artifact: Put a +1/+1 counter on each Goblin you control.
Whenever an artifact is put into a graveyard from the battlefield, you may pay {R}. If you do, create a 1/1 red Goblin creature token. It gains haste until end of turn.