Torcaldi's Bane, also called Pletra's Tear, was the name of a rift on Torcaldi that was draining the life force of the Torcaldians. Many Torcaldians were frozen in time, while others were captured by Balthar's people, who used their life force for themselves.
The Torcaldians told the First Doctor that the rift first appeared during a musical performance. The Doctor repaired their computers and recorded the music that was playing when the tear opened. (PROSE: The Ruins of Time)