The original working title of the series was "Semiautomagic."
Also, if we're including theories:
Theory 1: Merlin is in Demonreach. At the beginning of Skin Game Harry talks to a prisoner he says seems very British, and is absolutely at the lowest emotional low. Merlin has done some SHIT, I think he locked himself away because he thinks he deserves it. Harry will let him out and Merlin will teach him. Time magic definitely is gonna come from him. Plus, Ebenezer has Merlin's journals and Harry learned from them, having it from the tap is the next step.
Theory 2: Mac is an Outsider. Sharkface from Cold Days knew him, andMac definitely ain't vanilla mortal. The two Outsiders we've seen are He Who Walks Behind and He Who Walks Ahead or something like that. Mac is He Who Walks Beside.
