In an alternate timeline shown to Jean-Luc Picard by the Eleventh Doctor, Cybermen were converted from the inhabitants of Qo'noS, homeworld, of the Klingon Empire, by 2418. The cyber-converted Klingons were seen occupying the First City. This timeline, a combination of N-Space and the Federation universe, was averted when the Doctor and Picard stopped the Cybermen before they could conquer the Borg Collective in 2368. (COMIC: Assimilation²)
The cyber-converted Klingons were externally similar to the Cybermen responsible for their conversion; (COMIC: Assimilation²) resembling those made by Cybus Industries in Pete's World, these Cybermen of N-Space were associated with the Cyber Legions. (TV: Rise of the Cybermen, A Good Man Goes to War)
Notably, the converted Klingons were distinguished from other Cybermen by their distinctive Cyber-helmets which matched the unique shape of the Klingon head, with extensions reminiscent of hair. In addition, their chest plates were adorned with the Klingon insignia.