Must've drank a lot of milk
The mist that was inside the skeleton was morphing not making any sound but it could be seen violently thrashing around, till it finally took a form extending from the skeletons body and enveloping it.
The armour the skeleton wore had been covered in this purple mist till finally it gripped around the body and slowly turned into a midnight purple armour. Eventually all the pieces of armour had turned into this midnight purple armour with additional pieces, the extended parts of the mist had turned into extra arms for the skeleton.
The skeleton had dropped his great sword and the purple mist began to extend further into the hands of the skeleton creating pure black swords. The swords were rather normal looking except the hilt, the hilt looked like a pair of demon horns and was emanating a slight purple light.