Iskender-B199, known under the callsign HELIOS, was a Spartan-III Headhunter of Beta Company along with his older twin brother Ahmet-B198 during the Human-Covenant War. After losing their parents during the Battle of New Constantinople, the twins volunteered for the Spartan-III Program. Ahmet and Iskender, proved to be a hyper lethal duo above and beyond their fellow Spartan-III's and the two were eventually selected and removed from the rest of Beta company to be part of the secretive Headhunters unit. The two's close bond as twins made their matching rate a astounding 98.1%, the highest in the entire Headhunter Program.