sentences:  He first appeared in "Invasion of the Bane", the 2007 New Year's Day première special, and has appeared in all the stories except "The Eternity Trap".Mr Smith is a Xylok, a member of a crystalline race which crashed to Earth as a meteorite some 60 million years in Earth's past.It was trapped underneath the surface of the Earth until the eruption of Krakatoa brought a single, small Xylok to the attention of geologists.