The six-part prequel to Blood and Sand will chart the gladiator's days in the Ludus, overseen by the sinister Batiatus (John Hannah).
"Gannicus is a very self-destructive character," Clare told IGN. "He's always trying to escape his reality and he does that through... abusing things like alcohol in excess. There's a lot of contradictions in the character."
The actor said that he had modelled Gannicus's confidence and on-stage charisma on professional boxer Anthony Mundine.
"[Gannicus] uses the crowd like Anthony Mundine does," he explained. "He's a very destructive character, a self-destructive character, and he's also probably got suicidal tendencies."
Though Gannicus did not appear in the first season of Spartacus: Blood and Sand, series creator Steven S. DeKnight previously denied that the character was certain to die in the new prequel.
Spartacus: Gods Of The Arena begins on Starz on January 21.