Species bond

A species bond existed between each Lupari and their designated human. The bond's purpose was to save them, and the Earth against an event called the Flux. Karvanista was bonded to Dan Lewis. (TV: The Halloween Apocalypse)

While they were species bonding, the Sontarans got behind the Battalion wall in the milisecond before it was made and launched temporal attacks across time. (TV: War of the Sontarans)