How to get there: In each starting town’s graveyard, at the edge of town. Look for the grey-stone crypt entrance among the gravestones.
Stand by the crypt entrance and enter. The upper floor is a deep hall of ossuary galleries: twelve skeletons (Combat 12), six big skeletons (Combat 32) and three Skeleton Kings (Combat 60). The hall where you arrive is safe; the bright stone arch at its north end returns you to the graveyard you entered.
Steps on the eastern side of the deep hall lead down to the lower floor, where the Bone Sovereign (Combat 140) waits. The northern stair landing is safe. Each crypt has its own creatures and its own boss, so other towns’ crypts are not affected by your fight.