This started out as a 21-minute instrumental piece called "The Tower." When Fish joined Marillion, he was presented with the current set and asked to provide lyrics. At the time, he had been reading a book called Grendel by John Gardner, which examined the Beowulf legend from the monsters point of view. As the lyric took shape, they began to reflect Fish's views on what he calls "The hypocrisy of religion in dealing with murder and war."
The recorded version of the song is 17:40 long, while the live versions regularly ran to over 20 minutes. Often when it was played live, Fish, wearing a tattered cloak and Anglo-Saxon mask, would during the climax pull a member of the audience onto the stage and mime out his dismemberment. This was captured on the video EP featuring "Grendel" and "The Web." The song has not been played live since the band opened with it at the 1983 Reading Festival (recorded by Radio 1 and available on various bootlegs).
Suggestion credit: Jim - Mansfield, England, for above 2