Siege Perilous

In Arthurian legend, the Siege Perilous (, also known as The Perilous Seat, Welsh: "Sedd Peryglus") is a vacant seat at the Round Table reserved by Merlin for the knight who would one day be successful in the quest for the Holy Grail. The English word "siege" originally meant "seat" or "throne" coming from the Old French "sege" (modern French "siège"); the modern military sense of a prolonged assault comes from the conception of an army "sitting down" before a fortress.
In Thomas Malory's 1485 book "Le Morte d'Arthur", in an account taken from the Vulgate "Queste del Saint Graal", the newly knighted Sir Galahad takes the seat in Camelot on Whitsunday, 454 years after the death of Jesus. The Siege Perilous is so strictly reserved that it is fatal to anyone else who sits in it. Another version of this story is related in Alfred Tennyson's "Idylls of the King".
Originally, this motif about the seat and the grail belonged to Perceval, but the Lancelot-Grail Cycle transferred it to the new Cistercian-based hero Galahad. It appears, for example, in the earlier De Boron "Didot Perceval", where Perceval occupies the seat at Arthur's court at Carduel. According to many scholars, the motif of the dangerous seat can be further traced to Welsh, Cornish, and Breton mythology, whence the bulk of the Arthurian legend was derived. According to this theory, the Siege Perilous was a half-remembered version of a Celtic kingship ritual that has parallels in the Irish Lia Fáil.
Marvel Comics, adapting various Arthurian elements into their plots, used "Siege Perilous" as the name of a magical device. 