From DivNull RPG
This black granite box, about the size of a hat box, may have been created by the Galchutt when they actively roamed Praemal. It radiates negative energy as if the center of a desecrate spell. Its true power, however, is revealed when a lich's phylactery is placed inside it. When the box is closed, the phylactery is protected from divination as if by a sequester spell. Further, should the lich's body be destroyed, it is quickly remade into an idealized form. The body reforms in 1d10 hours, gaining two additional racial hit dice (d8's, as per the lich template), an additional +2 channel resistance, and an effective caster level two levels higher for the purposes of determining spell effects. These bonuses apply any time the lich's body is rejuvenated, but are not cumulative. If the phylactery is not in the box when the body is rejuvenated, the new body does not gain these bonuses. Only one phylactery may gain the benefits of the box at a time.
The osseous redoubt was stored in the Banewarrens without a true appreciation for what it actually could do. Thinking it was merely a desecrated box, it was stored in the outer vaults, as a container for the remnant crown.