In chapter 9 Grendel ends a reflection on the disappearance of religious conviction with this line: "The will to power resides among the stalactites of the heart. (Her-kapf.)" (128)
In a message to the John Gardner Discussion List (now defunct) on 9.11.00, Joan Gardner (mother of Joel and Lucy to whom the novel is dedicated) writes:
In this light it would appear that Gardner is either intruding upon his novel (disrupting the narrative dream) in order to comment on his own words, or he is using this personal allusion to show Grendel observing (and critiquing) his own thought. The latter seems to be the more likely case.