The mutated homunculus also known as homunculus S is an advance version of the current homunculus that alchemist class have. Little has been known with these summons because only few players were able to meet the requirements. In order for the homunculus to mutate, we need a level 99 evolved and loyal Vanilmirth, Lif, Filir, or Amistr homunculus. They can be changed to one of the mutated homunculus namely Bayeri, Dieter, Eira, Sera, Eleanor. From what I read. the skills of your current homunculus will remain upon mutation and the succeeding skills will depend on the mutated homunculus you'll choose. The list of skills has been released already but there are no information regarding which skill belongs to which mutated homunculus yet. Written after the break is my wild guess of the arrangement of their skills.