This is a hallowed burial site marked by the mythic menhirs (stone circles) of Faerûn, reputedly constructed in ancient times by the Yuir of Algarond and used to travel over long distances.
Recently it was taken by Anchorites of Talos and made into a summoning circle for the horrific Gorthok the Thunderboar, a minion of the god of storms and destruction: Talos.
Long ago the heart-turned-emerald of the buried warrior-priest (or wizard-king) was stolen from the tomb and only recently returned to the site by Our Party, having retaken it from a Night Hag within Montarthas Manor.
(See: wiki)