Eisen, the Ebon Rock (Japanese: 黒鉱のアイゼン, Kurokō no Aizen) is a Tyrant in Xenoblade Chronicles X. It is a member of the Petramand family. It can be found at level 51 on a rock in the lava river east of Ruined City of O'rrh Sim in Cauldros at night. Defeating it is required to complete the eponymous basic mission Eisen, the Ebon Rock.