Thanasis was the manager of gladiators Kosey and Wamukota, the former being trained by him since the age of eight and becoming one of his best fighters, earning him fame and money through Kyrenaika and Egypt. Sometime prior to 47 BCE, Kosey, desiring to spend time with his wife Hesper during and after the birth of his son, requested his release from his duties. However, Thanasis refused his request, due to the amount of fame and money he had gained through Kosey. He would later hire Egidio to help him train his gladiators and ensure they would not run away from his services.
That year, while on the journey to the Cyrene Gladiator Arena, Kosey collaborated with the bandits in the Green Mountains region to fake his own abduction, resulting in the capture of Wamukota and ensuring his own freedom. Egidio, however, was able to escape the ordeal and he reported back to Thanasis in Balagrae. Dismayed at the loss of his two gladiators, Thanasis enlisted the service of the Hidden One and Medjay, Bayek, to locate and retrieve them.
Bayek eventually did so and reported back to Thanasis in the arena in Cyrene, bearing news that Thanasis was not contented with; Wamukota had suffered injuries during his capture and Kosey had refused to return to Thanasis' service. Desiring not to lose face to his Roman competitors, Thanasis proposed a deal with Bayek, requesting him compete in the arena in exchange for Kosey's freedom, which he accepted.
While Bayek fought the arena, Wamukota returned to Thanasis outside the arena, providing him with information on Kosey's whereabouts. Thanasis decided to break his deal with Bayek, hiring several Roman soldiers and travelling to the lake in the mountains to find Kosey. Arriving at the lake, Thanasis was able to subdue Kosey, threatening his wife and daughter's safety if he did not comply. However, Thanasis' treachery came to an end when Bayek followed his trail, and joined forces with Kosey to defeat Thanasis and his soldiers, thus securing Kosey's freedom.
- Thanasis is a short form of the Greek name Αθανασιος (Athanasios), meaning 'immortal'.