Omniparadox

An omniparadox appeared to be a ball of shining light, but was a complex space-time event made by the collision of time.

The Eleventh Doctor sent the Sixth Doctor and Peri to the Santa Maria in 1492 to retrieve an omniparadox that would be created on the ship. The Bovine Herd Leader was trying to divert the Europeans so they would kill the Native Americans that were destroying the buffalo. The Leader's future self travelled back in time to warn him of the disastrous results of his plan. However, this led to the Leader in 1492 being killed, which meant his future self never travelled back in time, thus creating the omniparadox. (AUDIO: Trouble in Paradise)

The Sixth Doctor stored it in the TARDIS so the Eleventh Doctor could use it later to escape the Creevix trap. (AUDIO: The Time Machine)