Although the actual-titled Necropolis story ran for 26 issues, it was in fact part of a Democracy storyline which began four years previously. Dredd had defended the Judicial system he represents from democratic marches, although he became disillusioned due to the underhand tactics the Judges used to stem the marches.
Three years after the marches, Dredd finds a letter, addressed to him, from the body of a young boy, who was murdered. The letter, although written with naivety, highlighted several problems with the Judicial system which Dredd was already aware of, and concerned about, and ultimately felt responsible for the boy's murder, as he was en route to post the letter when he was murdered.
Kraken, a clone of Dredd, but was previously under Judda influenced, was rehabilitated and due to be assessed by Dredd for his full Judge assessment. Despite performing in his exam impeccably, even helping Dredd to remain calm when his mentor, and own assessor, Judge Morphy, was murdered, Dredd failed Kraken, proclaiming 'A leopard can't change his spots. Not this one, anyway.' In the same moment, Dredd also resigned effectively immediately, and requested to take the long walk.
After Dredd left, Chief Judge Silver faked Kraken's death, and kept Dredd's resignation secret from the public, to instil Kraken as a replacement for Dredd, regardless of his failed assessment by the departed Dredd. Kraken was easily manipulated by the Sisters of Death, who had attacked and left Dredd for dead in the Cursed Earth in The Dead Man saga, to bring about the Dark Judges; Judge Death, Mortis, Fire and Fear. They would go on to wreak havoc in Mega City One, creating their own Necropolis, with life the ultimate crime. Kraken was also made a dark judge for the duration of the Dark Judges' reign.
Dredd, who had regained his memory, returned from the Cursed Earth along with ex-Chief Judge McGruder, as Dredd felt that something was wrong with the city he once served. The dark judges had soon taken control of the remaining judges, who were now executing citizens, often committing suicide or succumbing to disease or starvation. Dredd and McGruder met with a group of cadets who were in hiding from the dark judges, along with PSI Judge Anderson, and a plan of action was formed. Firstly, Dredd killed fellow judge Kit Agee, who had been used as a psychic bridge for the dark judges to return. This caused the remaining judges to return to normal, free of the Sisters of Death's control.
With the judges now together and able to form a unit, they began to capture the dark judges. All but Death himself were captured, who had flung himself from a city block down into the city bottom, and vanished among the sixty million dead from the dark judges' tenure.
Judge Kraken, now free of Death's control, accepted his execution at the hands of Dredd.
Among the chaos of the dark judges' reign, Chief Judge Silver was killed and then reanimated as a zombie.