Seeing as I start a lot of threads that lead to heated arguments, I figured I'd put another one into the mix.
We know that Pietten was "marked" by the ur-viles in LFB, and that the marking was probably connected to his later insanity and blood-lust. In PTP, the ur-viles press their red blades against Covenant's forehead to knock him unconscious, and later, when cleaning the wound there is this said:
So was Covenant simply physically scarred by the ur-viles' actions, or was there something deeper that they did to him? Later in the story, Foamfollower fears that the injury might explain why Covenant allowed the ur-viles to put shackles on him in Foul's Creche, but we later understand (I think) that Covenant wanted to face the Despiser and so didn't object to those actions."Ur-viles!" Foamfollower muttered at Covenant's injury. "This will not heal. To make you captive, they put their mark upon you."