— Announcement spoken by Einzig to all Ex-Machina, No Game No Life: Zero
Like all Ex-Machina, Einzig resembles a young, attractive member of Imanity with some mechanical parts exposed. He himself looks like an Imanity male with striking red hair. In the light novel, he has a scar on his nose he got during the Great War. Despite being more than 6000 years old, comparable to non-aging Jibril, he looks only slightly older than Sora in the latter's view.
He initially wore a funeral dress-like black cloak when he first addressed Riku Dola to bring an end to the ancient war. However, by the time of his re-appearance in the Elchea Kingdom, he changed his outfit by dressing in similarly colored yet more casual butler outfits, only wearing the cloak when traveling.
As the Ex-Machina have a shared mental connection, he refers to himself or themselves as "worse than mindless machines". "Einzig" is a call sign for him and his predecessor units rather than an individual's given name. Originally blunt and cold, he later feels warmer about himself and the Ex-Machina after Schwi programs feelings into him and the cluster, causing him to feel grateful.
Much like Riku, Einzig acts like a cold, emotionless figure to accept the self-sacrifices of his brethren. He buried his grief deep in his heart in order to stop the war but actually cared about his clusters and could even name individual units.
It was revealed to Sora that due to reflecting Schwi's feelings toward Riku, Einzig developed an attraction to the Imanity king due to his striking resemblance to Riku. He frequently called Sora affectionate pet names and was even able to find his entire hentai collection.
"We are machines, tools bereft of heart. We have lived here, yet were never alive. Let us die having lived." - Einithi, At the end of the Eternal war.
- "Einzig" isn't a name for the male Ex-Machina, but a title for the administrator unit, which means Einzig inherited his title and role from his predecessor and can possibly pass it to next administrator unit.