Avengers (1963) #401

The Avengers team-up with the X-Men to take down Onslaught. The teams track down Magneto, believing he is at fault. The team discovers that Magneto is now "Joseph", a de-aged and amnesiac version of the X-Men's foe. But why is Rogue fighting the Avengers tooth and nail to protect Joseph? And is this "de-aged Magneto" really the man he claims to be?