User: Saber
Avalon, the Everdistant Utopia. The name of Excalibur’s sheathe, which also holds power as a Noble Phantasm. Aside from healing the user’s wounds and halting their aging, it also turns into a perfect fortress that protects against all physical interference when activated. Even in Arthurian legend, Excalibur’s sheathe is a “magic sheathe”. After Arthur received Excalibur from the fairy of the lake, he was approached by the wizard Merlin, who bequeathed upon him an enchanted sheathe. It is said that as long as he possessed this sheathe, he would not spill so much as a drop of his own blood. As such, it was even more valuable than Excalibur, and its loss to the machinations of his half-sister Morgan Le Faye is connected to King Arthur’s death.

Fate/complete material II; Weapons: Excalibur's Sheathe, pg. 119