[[WMG: In the end, Holly is possessed by the spirit of [[spoiler: now-deseased Sally Bones]].]]
That's why one of her eyes is blue.

[[WMG: Jalal and Sally Bones aka Saliya of the North [[FoeYay had]] [[MerlinAndNimue a history]].]]
They were lovers, and he [[spoiler: taught her the Way]]. Then she found out about his bidding relatonship with the other cat, who was the Paw's female ancestor, got jealous, and [[spoiler: killed him at the first opportunity]] (already after he sired a child with the said cat). Poor Varjak, he spoke to someone who banged his ancient ancestor.