BioWare stated on the Black Isle boards that the Viekang thing would be explained in ToB.
My thoughts:
I really have no idea...

Honest.
Perhaps he's a Bhaalspawn himself, although that would be kinda weird since he was struck by lightning when he saw you. If you went and talk to him with an NPC, he says that he's called "the Lightning Rod"

. He could also be fleeing Tehyr or something, as that's where the Bhaalspawns are duking out (and where
I'll duke
them out good

).
However it may be, it will sure prove to be interesting to say the least. Kind of like the pantaloons enigma, that's been troubling me since BG1 it has... can't wait to find those Nickel Panties... them Silver Pantaloons should've been called Pantalets thoug, if you read the Golden Pantaloons' description... but I'm ranting... and you can't help it... but I'll stop... right after this sentence... which is right now... now.
I remind myself of Jan, sometimes...
*shiver*
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GameBanshee, where I shall be a moderator, one day...