Hey,
Taking control of the character that Magic Charms is on does not take control of Magic Charms. My Magic Charms on a character that was mine that you now control, continues to protect my magicians until my next preparation phase. I cannot use the discard to capture ability while my magic charms is on a character I don't control. On my next preparation phase, if I still do not control the character Magic Charms is on I must either deactivate it, activate it on a different magician that I do control, or activate it on my artifact pile.
Tschow,
Tim "Sir Nobody" Maly