The powers of Darkness changed his body dramatically, giving him sulphiric Golden Eyes and caused a deeply tanned skin to form overtime, his physical strength also dramatically increased that he could crush a Knight's helmet with his bare hands. To add to his problems however was the fact that his body was old and was only retaining its strength because his control over the Darkness, Xehanort learned that he could not gain his full power unless he gained eternal youth which was impossible in his current aged state. as a somewhat feeble old man, certainly deceiving given his absolute power.