Necros Incident

The Necros Incident was the Time Lord designation for the event in which the Sixth Doctor confronted Davros on Necros, which they identified as taking place in the 47th century. (TV: Revelation of the Daleks, PROSE: Dalek Combat Training Manual)

Prelude
Davros, original creator of the Daleks, decided to turn on his creations, deeming them failures after they had lost their war with the Movellans. He unleashed the Movellans' virus on the Daleks which had rescued him in the hopes of him curing the virus. (TV: Resurrection of the Daleks)

After his attempt to exploit Lorraine Baynes' company was foiled by the interference of the Sixth Doctor, (AUDIO: Davros) Davros made his way to Necros. There he established himself in the Tranquil Repose as the "Great Healer", secretly exploiting the patients being kept in suspended animation by using them as subjects to be mutated into a new race of Daleks. (TV: Revelation of the Daleks)

Aftermath and legacy
En route to Skaro, the ship carrying Davros crashed on the planet Lethe. Davros set himself up as "Professor Vaso", altering the perceptions of the humans on the colony so they would not recognise him as the "Great Healer". He attempted to create a new machine, a Juggernaut based on a Mechanoid design. Under his Vaso guise, he also "befriended" Melanie Bush, whom he saw as a skilled programmer.

Lethe's atmosphere prevented the Supreme Dalek retrieving Davros directly, but its forces intercepted the Sixth Doctor's TARDIS, forcing him to serve as an agent of the Daleks and stop Davros's researches and manipulations. The Doctor discovered two of Davros's Necros Daleks had survived the crash, but were destroyed following Davros's final gambit on the colony and the Supreme Dalek's intervention. Davros himself was left badly injured by Mel after she reprogrammed several Juggernauts into attacking him, and his self destruct system in his chair was activated leading to the destruction of the colony. (AUDIO: The Juggernauts)

According to some accounts, Davros was then taken to Skaro, to be put on trial by the ruling Dalek Emperor (COMIC: Emperor of the Daleks!) and a jury of Daleks. (PROSE: The Shoreditch Incident) The Time Lords would later question if several of the Daleks Davros had created on Necros were present on Skaro during this time, helping to explain how one portion of the Dalek race eventually accepted him as their leader after the trial. (PROSE: Dalek Combat Training Manual)

Following his capture on Necros, Davros was transported to Skaro. One account held his trial was a trial of leadership, with him being granted command of the Daleks after a show of loyalty in exposing a Thal spy who had infiltrated his transport en route, revealing she had supplied him with a sample of the Movellan virus that he had chosen not to unleash. (AUDIO: The Davros Mission) Another had Davros being put on trial for his crimes before the Dalek Emperor, only to escape to Spiridon with the aid of the Sixth Doctor, who was playing his part in a scheme of his future self. On Spiridon Davros rediscovered an entombed Dalek army which he converted to his control. With this army he faced the forces sent by the Emperor to recapture him and invaded Skaro, claiming the title of Emperor for himself and instigating the Imperial-Renegade Dalek Civil War. (COMIC: Emperor of the Daleks) Davros' Daleks, known as the Imperial Dalek faction, matched the colour scheme of those he had originally created on Necros. (TV: Remembrance of the Daleks)

"The days of Davros and his humane work on Necros" were recalled by Seg of the Orcini New Daleks. (PROSE: War and Peace)

Behind the scenes
The Discontinuity Guide claims that Davros arrived on Necros 100 years following his rescue by the Daleks. It goes on to speculate that, whilst under interrogation during his incursion on Skaro, the Fourth Doctor had told Davros about the Human Factor Incident, which influenced him to convert humans into Daleks on Necros, Davros' conclusion being that, by possessing some of the Human Factor, the Daleks will not be slaves to logic and thus not be drawn into an impasse as they had with the Movellans.