I've searched and not sure this has been discussed in its own thread before, but I noticed this in a re-read of ADWD.  When Tyrion and the crew of the Shy Maid are sailing through the Sorrows, a lot of time is spent discussing Garin's curse, the Stone Men, and the Shrouded Lord.  Garin's curse of course, according to Tyrion, is Greyscale which further connects the Shrouded Lord and the Stone Men to the goings on at the Wall with Val and Shireen.  According to Ysilla, Garin's curse arose from Val