Whatever info I see, it's vague. Some say he can be found in all missions, some say in specific ones, some say it's only in Worlmen Sepulcher.
Can I safely assume that he and only he drops the rare items affiliated to him?
Can only level 36 toons find him, or are there lowbies that have found him as well?

Is it advised to only farm specific missions, should you want to find him or any item he drops?
I'm sure not just me would appreciate some info on this one, thanks for anything you can give me