Rift Quest:An Innocent Condemned  

The location on the map got me attacked by a zombie who happened to be THE zombie to drop the key, but we are not 100% sure that was the only zombie that could have.

When you open the cage, Azdea says "Thank you for freeing me, hero, but now your usefulness has come to an end.", followed by a flash of light and... nothing much. We think this encounter is bugged, slightly, but the quest did update so no-harm, no-foul.