Quote Originally Posted by Prototype909 View Post
He has Curtana, the same way all of the NPCs throughout the questlines have relic weapons. For example Estinien has Gae Bolg even though you can later forge it yourself, likewise Jehantel has the Artemis Bow and so on. At the completion of the Paladin events he even says "Though the monetarists may have stolen Oathkeeper... etc." implying that it's not in his possession unless I'm not remembering him recovering it sometime before the final Paladin quest.
Actually it's more likely that Solkzagyl has one of the two sister blades, either Joyeuse or (more likely) Durandal. Remember, unlike some other relics, the Curtana is a unique item, like the Thyrus (the one specific staff owned by A-Towa Cant and plundered from his grave).