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 token: Draw a card.")

Legality