Out Cold

This spell can't be countered. (This includes by the ward ability.)
Tap up to two target creatures and put a stun counter on each of them. Investigate. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Curious Inquiry

Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, investigate." (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Lazav, Wearer of Faces

Whenever Lazav attacks, exile target card from a graveyard, then investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Whenever you sacrifice a Clue, you may have Lazav become a copy of a creature card exiled with it until end of turn.

Cold Case Cracker

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

Foul Play

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

Case of the Filched Falcon

When this Case enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
To solve — You control three or more artifacts. (If unsolved, solve at the beginning of your end step.)
Solved — {2}{U}, Sacrifice this Case: Put four +1/+1 counters on target noncreature artifact. It becomes a 0/0 Bird creature with flying in addition to its other types.

Magnifying Glass

{T}: Add {C}.
{4}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw 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 this creature is turned face up, until end of turn, whenever a creature you control deals combat damage to a player, investigate.

Deduce

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

Blink

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I, III — Choose target creature. Its owner shuffles it into their library, then investigates. (They create a Clue token.)
II, IV — Create a 2/2 black Alien Angel artifact creature token with first strike, vigilance, and "Whenever an opponent casts a creature spell, this token isn't a creature until end of turn."

Toxin Analysis

Target creature gains deathtouch and lifelink until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Hotshot Investigators

When this creature enters, return up to one other target creature to its owner's hand. If you controlled it, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Eliminate the Impossible

Investigate. Creatures your opponents control get -2/-0 until end of turn. If any of them are suspected, they're no longer suspected. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Forensic Gadgeteer

Whenever you cast an artifact spell, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: 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.