Resurrection madness was a side effect of resurrection by Resurrection crystals. Sith resurrection crystals usually made the mind of the Sith unstable for months after resurrecting. There were several degrees of the madness, which two were shown in the Jedi Warrior Trilogy. Darth Vader had a lesser form of the madness, which made him repeat phrases he had already said. He muttered a lot to himself. He was also very rebellious to Palpatine. It seemed to have cleared almost entirely by the Battle of Zarnoth.