Complex sentence: He exhibited berserk behaviour, and this, together with the description of his large and unattractive head, has led to the theory that he might have suffered from Paget's disease; at the age of seven, Egill was cheated in a game with local boys.
Split into simpler sentences: He exhibited berserk behaviour, and this, together with the description of his large and unattractive head, has led to the theory that he might have suffered from Paget's disease. At the age of seven, Egill was cheated in a game with local boys.