Anjeliqua Whitefriar

 was an old friend of Melanie Bush. The Master planned to use her to harness the power of the Lux Aeterna. Since this would have killed her, Kronos allowed her to merge with the Lux Aeterna, creating the Quantum Archangel.

She planned to create pocket universes for every living being and remove suffering from the universe at large. Unfortunately, there was not enough energy to do so. Once the Sixth Doctor managed to convince her of this, she abandoned the power she had obtained and became human again. (PROSE: The Quantum Archangel)