I was playing D3 in Hell with my Barbarian, and just finished getting the third sword piece of El’durin. As I saw Deckard Cain die and I exited his cabin, I saw a strange figure huddling between Leah and the entry to the cabin.

It was Deckard Cain!! Very much alive! I have taken a screenshot of this bug –

My Templar is confused on whether to kill this undead Cain or just be glad that he is back!