You just keep banishing him/her to Planer Arkam and he/she just keeps coming back to kill again.
You can't keep a good Time Lady down. Missy, AKA The Master (Michelle Gomez) will be returning to Doctor Who for the premiere two parter for Series 9. Here's hoping The Doctor can handle her.
They're filming the Series 9 premiere. Clara fans hope Miss Coleman will survive the ordeal.