sentences:  They were made undead by two witches, Phobia and Nausea, the Sisters of Death, who became undead themselves.Eventually acquiring the technology to travel to other dimensions, they came to Earth and attacked Mega-City One.They have been defeated by Judges Dredd and Anderson several times, but each time only after inflicting great loss of life, most notably in 2112 when they killed 60 million citizens and thousands of judges.