I had the players meet Artus and hang around for a while. I introduced the powers of the Ring of Winter (I thought about nerfing it to 6 charges instead of 12. It still would be very powerful. But the rules are not so relevant for an artifact of this magnitude.)... then Cimber having his own agenda, I had them part ways.
The Ring of Winter is a very coveted item (Frost Giants, Zentharim, Red Mages, Xandala...) , so Arthus might want to get away from the players for their own good. In the book "The Ring of Winter" (An excellent book.) a curse is attached to the Ring: friends and other people close to those who wield or seek the ring tend to meet a premature death. So you might want to have one or two of the minor npc in the group die to emphasise that fact and have a guilt striken Arthus discretly part ways, leaving a note or something...
Point is, I don't think Arthus is meant to be hanging with the players for ever. Any npc so powerful that he can repeatedly steal the spotlight from the players has to go away and take care of his own business at some point, the sooner the better