I wondered about that too - could never find anything... the only thing I noticed was the grate under the stairs leading to the slums - just underneath the order armorer and merchant. Now I can crawl through that into the sewers, but I don't know whether that's because of the key or I just missed it from before 
The other strange thing about this key is that it does not unlock the locked door in the house where you find the half-elf after freeing her. Plus there's another door in this house that, though it shows the 'door icon' does not react at all when clicked on. Anyone gotten through either of these doors?
No, but there are more locked doors in a few houses and they remain unaccessible and locked. Permit the owners their privacy, Geralt can't poke his nose into everything he wants to
That's odd. I never remember having problems getting back into this house. Someone else check this please. This key's use has recently been added into the wiki for this quest, and I'd hate to have it wrong.Are you sure we aren't misunderstanding each other? The bandit's key is meant to allow Geralt access to the house that the half-elf is rescued from, not any doors inside said house...lotjie said:
I entered one of the houses in the temple quarter near the hairy bear. There was some brute who offered me a quest to retrieve a treasure from the house. Yet there was no treasure, it was a trap. I killed the ambushers and freed the half-elf.The half-elf then told me to meet her (it was a she I think ^^) in the non-human quarter. I did have her on my map, but I didn't visit her rightaway. Now I can't seem to talk to her anymore and when I try to, she tells me something along the lines of "the diviner's wrath is terrible". Did I miss the quest she was about to give me somehow? What triggers her being non-responsive?
Indeed. In addition to this, the Half-Elf in question is an "ally", highlighted in green as opposed to the normal neutral blue.
She lives in the Dwarven blacksmith's house which isn't his shop. He has a seperate home in the non-human district. It's nearby Kalkstein's and Vivaldi's house... look here