Ok so I have finally finished reading the Red Queen and I am still a bit confused as to what the Ancient Promises are?
Swallow tells Elspeth that he has foreseen her speaking the words of the Ancient Promises in the place where they were first forged (between Cassy and the first Red Queen) and that he will be standing by her side at this point. He also tells her that he knows it was in the first place they were forged because he discussed the vision with his father who recognises the background scenery of a carving Swallow describes. Swallow however is not sure where exactly it is because in the vision it is night time and Elspeth is carrying a lantern.
The only correlation to this vision is at the very end of the book where Elspeth and Dragon are trying to find the slot for the Darkest Door to shut down BOT in Luthen's crypt which has carvings in it. However, by this point Swallow has already been murdered by Ariel so I don't really see how this fits. Also, the words she speaks don't really sound like an ancient promise.
Or is the ancient promise... I come unto thee Sentinel. Judge my hand and let me pass for all I have done was in your name. However again Swallow isn't any where near Sentinel, there's no carvings, its not night and no lantern...
Mod note: thread moved to Theories section.
I was somewhat under the impression that it was related to when everyone was in the chamber, and that is when he died. Not sure of what the actual words would have been though. But definitely a good question