Board Thread:Spoilers!/@comment-6175354-20150730230428

Adam Horowitz revealed that episode 5.03 would be titled Siege Perilous.

In Arthurian legend, the Siege Perilous (also known as The Perilous Seat) 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. 