Near the beginning of chapter 2 on the Iorveth path, after Spoiler:Saskia gets poisoned, Phillipa will say that she will need one of the 20 rings of power to cleanse the poison. Iorveth then remarks "One to bring them all and in the darkness bind them", and soon after Geraldt will also remark "and then I'll have to run barefooted to the top of a volcano." Which is a reference to the Lord of the Rings series.
Contributed by Milesthumbs