I thought it had a pretty clear answer - Sartar, being the highly unconventional Orlanthi leader that he was, brought the Telmori peace with the Sartarites and resolved their own leadership crisis. Presumably there was some clause for them to serve his descendants for his help, or maybe they swore to help him without prompting, or perhaps he told them some secret that made them realise they need to do this.
That said, consider my interest piqued. Does it go beyond this explanation?
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> This always felt weird. Why this devotion despite the hatred shown by almost all right-thinking Sartarites.
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> WF15 explains why - and why it is possible that one of the Argraths is a werewolf.
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> regards,
> Charles
>