As I've finally managed to take this guy down with trusty old berserker, I thought this was really a cool fight. You get that feeling of desperation as he keeps coming back and you'd barely survived through the previous form, you're thinking "This is just getting ridiculous, just die already!"
So yeah, nice work making this encounter, and congrats to all who succeeded in beating him to a pulp, those 6 times.
Here's some character ortraits of Namtar's three visually different forms i decided to make to celebrate his permanent death.
Hope you enjoy the Pit Nammy, because you're not leaving any time soon.