Focus for the maintenance of an Oblivion Gate to and from the realm of Coldharbor. It remains fixed in a position once the portal is opened, and the portal can only be closed by removing the sigil stone from its place.
If the portal is closed, the person who holds this stone may use its innate magical power once, to gain resistance to Necrotic damage for 1 hour. Upon use, the sigil stone is fractured and can no longer be used again.