As others mentioned earlier in this topic regarding Zodd's age, I was thinking why they call him "Immortal" might be more than just about his abilities in battle. Cant wait to find out more.
Well yes, that's how it's explained when he is first introduced. Mercenaries have called him that because he's been seen on battlegrounds for "almost a hundred years" and every time he's believed to have been killed, he shows up again. The idea that Zodd has been alive for longer than 300 years, a number he specifically mentions twice in the series (volume 5, volume 17) has very little going for it. It hinges on a single thing: the fact Zodd is familiar with the Berserk's armor. But there are other ways to explain that knowledge than him having been alive during the time of Gaiseric's empire.