The Hazandra, the Ghost of Love and Wishes, as named by the Apocalypse monks of the Andurax, was an "intuitive" gemstone that could draw energy from the nearest star to fulfil the desires of its owner. It was formed in the heart of a red hole and stabilised in pure dwarf star crystal. As of 1992, only four such stones remained in the universe.
The Twelfth Doctor planned to use the Hazandra as a power source for his "time distortion equaliser thingy". He gave the stone to a young Grant. However, mistaking the Doctor's instructions as meaning that the stone was medicine for his cold, Grant ingested it and gained "superpowers" which helped form his alter-ego, the Ghost. (TV: The Return of Doctor Mysterio)
The Twelfth Doctor and Grant later went to search for the stone's siblings. (COMIC: Ghost Stories)