Can't seem to find him. After searching infructuosly through the city I even looked up the game guide with the city map and specific supposed location of Iorveth. I had been there countless times searching and didn't find it, although I did find the room with Iorverths' troops. Anyway he isn't there in the entire old stone gate district and I cannot complete properly the succubus sidequest. Neither I can keep advancing on the triss quest because If I do, the succubus sidequest is marked as failed.

For me, he was in th elven district, or w/e it's called. The area with crappy housing and drainage. I'm guessing you know that already though. I believe there are two entrances to this area. Look to both of these entrances (not doors, just open pathways), he was standing to the left/right depending on if you're entering/exiting the area. If you still can't find him, either you are bugged like you say, or maybe the time of day is wrong. I found him during the day, not sure what time.

In any case, couldn't you just go kill the Succubus? Or do you have dark thoughts on your mind . . .? Heh

The elven distric has one entrance, but it's main "street" goes in a circle back onto itself. My dark thoughts are that I want to really solve this quest. The real culprit seems to be the elve, not the succubus (the blade fragment seems to indicate so). In other words I would prefer not to sacrifice innocents just to have the quest flagged as "solved".

Anyway it's really strange. I already asked gog to tell me how can I spawn Iorveth again, hopely to solve this problem. For now I keep doing the other quests, although I'm running out of things to do before the next step on the Triss quest. Another problem I seem to have encountered is that I have killed over a hundred harpies (have gone into harpy inhabited zones at least twice), I have bought and read the book about harpies, have got the harpies traps, but can't do anything with them. When equipped in a quick slot it doesn't show and R doesn't do a thing. Near the nest I don't get any option with the mouse to "arm" the trap. So in general I cannot finish that quest either. The gameguide speaks about a "firefly bomb" which you aim and destroy the nests that way. But as I told before I have killed so many harpies I should already have whatever "knowledge" required, but I don't seem to have it. In this case I may be missing out on something, so I'm still searching and for now I can't call this a bug. But if none of the merchants won't have the diagram to the firefly bomb, I suppose I will have to call this a bug too.

Found that the harpies trap needs a harpies lure. : ) In retrospective it's obvious. I will have to try it out if I can eliminate some nests that way. Anyway I cannot manufacture this harpies lure, and it seems I cannot buy more than four lures. None of the other merchants have it. So there is no way I can eliminate 7 nests. Will try anyways.

Nope, those traps are just an expensive decoy from the quest. I just armed and put one besides the magic tower nest (where you find the first dream crystal) and nothing happens. Well, I'm really missing something, or this is another bug in the game. I'm starting to think to leave this game for a while till the publisher irons out it's bugs. The game is not broken, but I seem to miss out on a lot of sidequests because of such bugs.

look inside the house where they gather outside the building. I've found him inside taking a nap.

This quest bugged out for me for a while as well. I knew where he should have been, but he wasn't there and the map marker kept jumping around depending on where I was (either entrance of stone gate as you say or behind the house he's supposed to sleep in). I just ignored the quest for a little while, restarted the game a few times, and eventually he was back where he was supposed to be. I would suggest focusing on some other quests first and then trying again later.

Spoiler:

Actually no it is not bugged, there are 4 harpy nests in the Quarry. The other three are in the cave that have 5 dream crystals (you will go to this cave later in the main quest)

Don't bother placing traps near the magic tower coz there are no nests there! :-)

Well I already went to the cave. Did everything before finishing the game : ). Near the magic tower there is one nest. It's the closest to the ground really. Besides I tried to use the trap near the nest at the bottom of the quarry without success. Nope, it seems this quest was bugged on my firs playthrough. I'm trying for my second time to see if there is a difference : ).

Well he does leave after the whole Stennis incident.

In my case I had precisely this problem, the pointer jumped from the human sector, to the dwarven sector, to the elf sector, to the main gate, etc. But Iorveth wasn't in any of those places. In the elf sector I searched both rooms (the one where the pair of elfs lived and the one where the soldiers headquarters were) multiple times without success. Iorveth appeared again when the royal blood quest started and went away as soon as I solved that quest (during the quest I couldn't talk with him about other matters). So I couldn't solve the succubus quest on that playthrough. Well that's what the second playtrough is for. : ) Hope I won't have the problem again.

In other news on this playthrough I found out of the way to save the prisoner (in my case Ayrian) in the torture chamber. Thought it would make a difference and he wouldn't blow up the castle. Sadly it didn't. Besides found out that may be it's not for the best to save him and his men in the prologue, as I loose the possibility to look at the baroness tits : ), besides what's the point if later he blows up himself anyway. May be next time I will rather duel with him : )

Regarding the Harpy traps, only use the traps when there are actually harpies attacking you . I've found placing the traps in combat worked like a charm, they will immediately pick the trap up instead of attacking you. I think the confusing part is only after the FIRST trap+nest destroy do you see how many traps you actually need (i.e. 1 of 7 nests destroyed) , before that the quest just says "use harpy traps" ...which is a little vague.

As for the Succubus thing, remember if you did not have surgical tools with you when you "analysed" the corpse, you can't complete this quest by talking to Iorveth. Iorveth is going to ask you for proof, and if you don't have it, you might as well ask the cat ;) (and yes, you can still get the surgical tools and go back to the corpse and re-analyse)

Iorveth also walks around in the area. To be more exact where he is, he is near the exit to the forest [where you analyse the corpses] . Usually inside the house right by the exit, and sometimes he's wandering in the area ... Best way to find him is to go to the house at NIGHT and look for him on one of the bed rolls on the floor...i've missed alot of NPCs because they sleep on the floor and you don't see them.

: ) Well the harpy case may be that the problem is I killed those irritating harpies while approaching each nest. So probably that's why the damn trap didn't do a thing.

Iorveth was a lost cause. Although in the beginning I really didn't know where he should be, later I knew very precisely the location, but he wasn't. Day or night he wasn't anywhere, until he was spawned in the royal blood quest. But then you cannot talk to him about the succubus. An later Iorveth leaves, so the quest is forfeited anyways. I did buy the surgical tools the very first time I arrived at the dwarven city. It was pretty obvious, when the description said "quest item". So when I did the examination of the corpses I retrieved the piece of blade automaticaly.