Their plan, or construction, of a pile of mountains atop which they would confront the gods is described differently according to the author (including Homer, Virgil, and Ovid), and occasionally changed by translators. Mount Olympus is usually said to be the bottom mountain, with Mounts Ossa and Pelion upon Ossa as second and third, either respectively or vice versa. Homer says they were killed by Apollo before they had any beards,[6] consistent with their being bound to columns in the Underworld by snakes, with the nymph of the Styx in the form of an owl over them.[7]