Probably a silly question, just wanted some clarification. In the rule book it says Formations are a special type of detachment. Does that mean I can take a formation by itself as a detachment or does my formation need to be part of a detachment? Say i have a CAD of from the Dark Eldar Codex, can I add a The Heroes Path formation from Harlequins by itself? Or does it need to be part of the Harlequin Masque detachment? I hope this makes sense.