I'm at Sigil Again part of the game.
I have completed the Curst Administration.
I can't find the Birdcage and the Siege Tower guy does not offer it.
Xander in the foundry keeps asking for the Blood and Skin!!!
for hes DREAM machine...but I already gave it to him.
Why not try pickpocketing Xander for the blood vial? Then you can give it back to him. Once he accepts it and starts asking for the birdcage, it will probably appear as an option in the conversation with the siege golem. I'm not sure if this will work, but you can give it a try. Just remember to save your game before you do, in case pickpocketing fails and Xander turns hostile.
Now, I must admit it's been a long while since I last played PS:T but IIRC it's not necessary to complete the dreambuilder quest in order to finish the game. Actually (please note, this may be a spoiler) if, as you say, you have already visited Ravel and travelled to Curst and Baator, you wouldn't be getting much out of the dreambuilder quest anyway as the 'dreams' refer to events that you have already experienced in these places. The dreambuilder was intended for players to complete before they activate the portal to Ravel.
Hope this helps.
'... And at other times it seems like that time is only a handsbreadth away, that I can almost touch it, that if I could put my arms around you or touch your cheek or the back of your neck, I could carry you away with me into a different future with no pain or darkness or bitter choices.'
