1. how to open it? with the "sewer key" from windspear hill? i have got that key, but the door still locked. please help. and what behind this door?
2. where to get the three parts of that kangaxx quest.

I'm not sure which inner chamber you mean. Which map are you on, the main one with interlocking tunnels? if so...

SPOILER>>>>>>>>>>>>
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1. The sewer key opens up a secret door that leads into the mind flayer dungeon which is accessed through the main part of the sewers near the northeast of the map. You need to find the Cult of the Unseeing Eye for the key to get to the Shade Lich which is part of the Kangaxx 'quest'. Gaal gives you this key.

firstly please excuse my english, i m native chinese.
and now i know what is the sewer key used for. and i understand why i can't get in that
"inner chimber" of the sewer under temple distinct. i killed Baal b4 he say a word to me! so i can't open that door, can't finishthe "lich quest" too.
i will restat my game.
really thanx for ur reply.

Umm...it might be a good idea to not kill everyone you meet at first sight. You'll have plenty of opportunity to kill people