[All]: The helmingr seems to be the second part of a stanza, introduced in R, Tˣ and W by the conj. meðan ‘while’. Ms. U has the introductory þás (þá er) ‘when’, which has been preferred by Skj B and Skald. Gamli describes Þórr’s smashing the World Serpent, Miðgarðsormr, with his hammer, Mjǫllnir, when they fought in the ocean.