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Can Necron lords detach from any unit they are in? I am not sure if this is in the rule book, but anyways ya
You knock 'em down, and they come right back up again ..... NECRONS
Yes they can. They might have to take a leadership test, im not sure, but i do know that you have to do it at the beginning of your turn, before/as your moving, and MUST let your opponent know.
In the moving phase, a character may join/leave a unit as soon as they leave/make unit coherency.
He is an independant character after all (and is subject to the independant character rules in the main rulebook).