Rune Dreamers

A Rune Dreamer is an individual afflicted with a mysterious ailment that causes visions of a particularly-shaped Ash Rune. 
Most of the nature of the Rune Dreamers' condition is of yet unknown, though observed symptoms include severe memory loss as seen in the Accursed Dreamer Trio and it seems to be ultimately fatal, as with Goshawk and his tribe.
The Stranger's dialogue seems to imply that he changed his opinions about many things in the world, especially the Contingency, in light of his Dreaming. It is unknown if knowledge was actually imparted to him, or he is delusional, which could be a possible symptom of the ailment that Dreamers suffer from.