The Resonance Engine was a Time Lord machine which served as a superior version of a neural amplifier, its plans hidden away inside the Matrix. Padrac had the Sonomancer locate the plans and had one built with the aim of using it to boost her powers and destroy the universe.
However, once she learnt how Padrac had used her, she transferred her powers to Helen Sinclair and had her crash a Battle TARDIS into the engine, destroying it and causing a temporal implosion which spread the Sonomancer across time and space and hurtled the TARDIS into the Time Vortex. (AUDIO: Stop the Clock)