It's pretty confused (as usual in Marvel) Basically, Magneto is hanging in Genosha, and is found by Xorn (yeah, /that/ Xorn) who... I'm really not sure what the whole exchange meant, but something like he needs Magneto and was kinda always his powers, so Magneto has his powers back now onloy not under his control. Then the Avengers come and he dies. Marvel logic.

Re-reading that, I realise that wasn't very helpful. It was in Avengers #20 if you want to see it for yourself.