Untempered Schism
It's a gap in the fabric of reality through which could be seen the whole of the vortex. We stand there, eight years old, staring at the raw power of Time and Space, just a child. Some would be inspired. Some would run away. And some would go mad.
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). The Schism appeared to consist of an opening into the vortex, contained by a circular ring. Before the Schism lay a plaque bearing the Seal of Rassilon.
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." Both the Doctor and the Master agreed the experience was a painful one.(DW: The End of Time - Part 2)
Initiation of the Master
According to the Doctor, many thought that it was this ritual which first turned the Master insane . 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).
It was at this time when the Master first heard "The drumming... the never-ending drumming."(DW: The End of Time - Part 2) that would plague him throughout the rest of his life, perhaps driving him mad. The drumming sound was in fact a signal sent back through time by the Time Lords, in the final hours of the time war, in an attempt to escape their destruction.
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 Series 1 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 vortex manipulator.
