Diego is a saber-toothed tiger that is part of a herd of animals after living out a number of experiences that united them all. Initially a cunning and remorseless hunter in a pack of other sabers, Diego was to deliver a human baby to his pack leader, Soto, as revenge upon the humans. during his interception of the child, Diego met a mammoth named Manfred and a sloth named Sid, who had already taken the child and, in time, convinced the saber to leave his old pack and join up with them as part of the herd.