In Arthurian legend, the Siege Perilous (Welsh: Gwarchae Peryglus, 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.[1]
...he shall be born that shall sit there in that siege perilous, and he shall win the Sangreal.