Elegos |
Shattered Star begins with the open knowledge that Runelords exist, that Thassilon was a thing, and that there might be more. It will talk in some places about Runelord Karzoug, in some detail. So your player might have some additional information about Karzoug, and his whole...thing. But probably not the biggest issue. Theres nothing in Rise of the Runelords that will spoil things written for Shattered Star that I can think of.
magnuskn |
Karzoug is mentioned quite a few times in the AP and chronologically the AP plays out after his defeat. Otherwise, no other Runelords appear in person, however you interact with a good number of their lairs.
wordelo |
there are some iconic thassilonian monsters in shattered star that are also in RotRL. I am DMing shattered star but never have played or DMed through RotRL. One of my players is playing that game at the same time, and he already knows about Karzoug, and runelords and such. He doesn't really feel spoiled and I still don't know very much about RotRL outside of some events (some big attack on sandpoint)
Shattered star is very fun though and it's also kind of a sequel to curse of the crimson throne (well one part is)