Haadhun is Kall's minion. The name is common among felguards. However, he does have more than one master - he is also bound to Tenebrais' will, and there have been furious bouts of competitive summoning between the two masters to gain greater dominion over him. Haadhun himself seems to find this amusing.
Doesn't speak. Prefers to stick his axe in things. Apparantly has no sense of shame and a cruel sense of humour.
Haadhun doesn't seem to have any nicknames. However, he is very picky about how it is pronounced.
Hard-hoon. Long oo sound. Not anything else. Or there's an axe in your head. (No, really.)
(Or, at least, he'd like to think there would be.)
Built like a brick wall. With an axe, and a sharp one at that.
Haadhun does not talk, so there's no way to really know about this. It's fairly safe to say that he probably has a more normal background compared to the rest of Kall's demons, at least - he seems to have an attitude considered better by most warlocks and their demons, too.
During his time in Azeroth under the control of the two warlocks, he has gained knowledge of both honour and strategy. However, he will give no consideration to either unless instructed to.
This name is common for felguards. At some point other felguards called Haadhun will inevitably cross your radar. They are probably not this one. Probably - you never know.