Premise: Excalibur is the ninth studio album by Grave Digger and is the final album of the "Middle Ages Trilogy". It tells about the story of King Arthur and the knights of the round table. The line-up for the backing vocals to this album included Piet Sielck, Hansi Kürsch, Hacky Hackmann + Boltendahl.
Hypothesis: Excalibur is the 6th  studio album by Grave Digger album of the "Middle Ages Trilogy