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After gaining access to the Matrix, Padrac observed projections of Gallifrey's future, and in each, it was destroyed by the action of war or the conflicts of other species. He wondered what would happen if the Time Lords became the only species in the universe, and the projections told him that Gallifrey would survive. Padrac then set out to gather a group of individuals who would help him in his quest to make the Time Lords truly immortal.
The Coalition obtained the Crucible of Souls to fulfill this purpose - when the universe collapsed the Crucible of Souls would convert what remained of the life energy of the races destroyed into regeneration energy.
After the Clocksmith's Doomsday Chronometer calculated and then brought about the end of the universe, the Coalition planned to use the Crucible of Souls to convert the life energy of the universe into regeneration energy. This would make them immortal and ensure the Time Lords would continue to survive. (AUDIO: The Crucible of Souls)
Padrac placed Caleera in the Resonance Engine in order to get her to destroy the universe and later captured the Eighth Doctor to be part of his plans. The Doctor managed to get Caleera to destroy the engine and the Coalition's plans were defeated. (AUDIO: Stop the Clock)