Altara's Scepter

Altara's Scepter is magical artifact which may be used to sever lines of magical power. It appears in  Ultima Underworld II and  Ultima IX.

Description
The sorceress Altara sought to assist the Avatar in their efforts to dismantle the Blackrock Dome enclosing Castle Britannia, and manufactured this wand on their behalf. To create it, she required that the hero bring her the egg casing of a dread spider and an amethyst rod, which she combined with a specially prepared black pearl she had already altered to suit her needs.

Once complete, the scepter was able to prevent the Guardian from drawing power from the various sites across the planes where he had invoked great magics before, which weakened his ability to maintain the spell which held Lord British's castle imprisoned. The Avatar used it eight times: at Bishop's prison cell in Tarna; in the engine room of Killorn Keep; at the great fountain of Anodunos; in the Bliy Skup Ductosnore's chambers in Talorus; at the entrance to the Pits of Carnage; at the site of a magical cave in within Praecor Loth's tomb and at the Shrine of Spirituality within the void. Once this was complete, the powers which fueled the structure of the dome were severely weakened, and the Avatar was eventually able to shatter it using the Horn of Praecor Loth.

Later, the scepter featured amongst the exhibits of Britain's Royal Museum, standing testament to this crisis in Britannian history and its eventual resolution.