This tomb is used to represent the thousands of heroes who gave their lives in the Rikti War.
The Seeker of the Unknown Badge is in the Moth Cemetery neighborhood of Dark Astoria. Approximately 160 west, and very slightly north, of the Moth Cemetery marker is a deep chasm. At the bottom of that chasm is a doorway that leads into a tunnel. The badge marker is outside the second (middle) crypt in that tunnel.
Its coordinates are (1,868, -80, 1,352).