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)

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.