Spire were gold-skinned warships constructed by the Time Lords and built for travelling through space with the ability to wipe out entire planets.
These spire-shaped vessels were constructed from solid gold as the inhabitants of Gallifrey had no concept of money. Thus, they made use of the substance as a building material and gathered from numerous points in the time zone. Closer examination revealed that the ship was composed of a lattice-shaped structure with numerous beams and arcs that were the size of houses. These were all interwoven together in a tight formation with only a few black spaces in-between the structures. Whilst holding an aerodynamic shape, it did not make use of fins or rocket boosters but instead twisted in a corkscrew manner from the nose end in a manner similar to burrowing style movement. (PROSE: Dead Romance)
Behind the scenes
These starships were never named in the novel but instead referred to as "spires".