Whenever you cast a creature spell with converted mana cost 3 or less, investigate. (Create a colorless Clue artifact token with ", Sacrifice this artifact: Draw a card.")
4/8/2016 Casting a spell for an alternative cost, such as a madness cost, doesn’t change its converted mana cost. For example, casting Twins of Maurer Estate (a card with mana cost and madness cost ) for its madness cost will not cause Bygone Bishop’s ability to trigger.
4/8/2016 The token is named Clue and has the artifact subtype Clue. Clue isn’t a creature type.
4/8/2016 The tokens are normal artifacts. For example, they can be sacrificed to cast Angelic Purge or targeted by Root Out.
4/8/2016 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 and sacrifice it to draw a card.