NOT PATHFINDER BUT!!!!!
A similar type of undead warrior was seen in the Forgotten Realms campaign setting. A paladin by the name of Miltiades was condemned by Tyr to exist as an undead knight for using dishonorable assassination tactics to kill his enemy Zarl. Miltiades retained his sense of good and fought by the sides of good heroes, helping to defeat the forces of Bane. He was eventually restored to life by Tyr after helping the heroes destroy a pool of darkness and a pool of twilight.
http://forgottenrealms.wikia.com/wiki/Miltiades
