Xanu
From superman.nu: Supermanica
Xanu
An evil extra dimensional scientist and would-be dictator who inhabits a bizarre world enterable from the earthly dimension by means of an antique mirror, apparently “made centuries ago by sorcerer from their world or ours,†which serves as “a door between the two worlds.’ Entering the strange mirror-world with Batman and Robin in November 1961 in hopes of curing Batman of the freakish qualities he acquired during an earlier visit there, Superman defeats the evil Xanu and puts an end to his dictatorial ambitions (WF No.121, Nov 1961: “The Mirror Batman!â€). (TGSB)