Something about this investigation that is intriguing are all the references back to the same theme of the devil.  The "beast" reference to the devil is mirrored in Lily's "devil's lantern" tombstone flower, the surname "Gray" is associated with the devil, and Elmer died on Halloween, which has obvious connections.  I was not able to locate any legends about dying on halloween, or any meanings therein.  Perhaps none of these things have any bearing on the meaning of the inscription, but are quite coincidental nonetheless.