When Thraben Inspector enters the battlefield, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
If you sacrifice a Clue for another card's cost or effect, such as that of Angelic Purge or Tamiyo's Journal, you can't also pay {2} and sacrifice it to draw a card.
The token is named Clue and has the artifact subtype Clue. Clue isn't a creature type.
The tokens are normal artifacts. For example, they can be sacrificed to cast Angelic Purge or targeted by Root Out.