I understand that I can simply change the canon if I need to, but I'd like to work inside the established world as much as possible. Is there any potential for a major religious conflict on Lythia?
Well, canon is "as of 720 TR". Just proceed one day further and call for an escalating "religious motivated conflict" on mainland Lythia or even an internal temple war over there.
Let some religious instance summon all their faithful warriors for support and your SCs belong to the delegation sent by the Hârnic temples. So, they will have plenty of opportunities to explore Lythia. Perhaps, the initial call was even a fraud to lure them away?