Untempered Schism

The Untempered Schism was an opening into the space/time continuum, "a gap in the fabric of reality from which can be seen the whole of the Vortex" (DW: The Sound of Drums).

Use in Time Lord Initiations
It was used by the Time Lords in an initiation ceremony for young initiates into the Time Lord Academy. The Gallifreyan children subjected to its terrifying effects would react differently - "Some would be inspired, some would run away, and some would go mad."

Initiation of the Master
According to the Doctor, many thought that it was this ritual which first turned the Master to evil. As a child, during his initiation, he gazed into the Vortex, and saw the raw power of time and space - "That's when the Master first saw eternity." (DW: The Sound of Drums)

Initiation of the Doctor
The Doctor suggests that his eight-year-old self was one of the ones who ran away--indeed, that he never stopped running. (DW: The Sound of Drums)

Behind the Scenes
The "time tunnel" effect seen in the Untempered Schism, and reflected in the eyes of the young Master, is the same graphic used in the opening title sequence of the TV series since Season Twenty-Seven in 2005. It was also used at the opening of The Sound of Drums to represent the transit through the space-time continuum with Jack Harkness's time bracelet.