Galvoln (ガルヴォルン) was a magic metal from YGGDRASIL.
In the Web Novel, the metal is a standard component to the maid outfits worn by the Pleiades. The skirt of the maid outfit possessed a magic black metal board over it, increasing its defensive properties. The board and even Yuri Alpha's chest-plate were made of the same material which was composed of three metals: magically enhanced steel, Adamask metal, and Galvoln.
No information is given on its appearance.
So far it is only described as a magic metal.
- In the Web Novel, the composition of the maid outfit is described however in the Light Novel its materials are omitted.