Frontier in time

The frontier in time was the edge of the Great Houses' noosphere in the universe's far future, past which they could not see or safely travel. The frontier appeared as the posterior end of recordable history in the Spiral Politic and obscured the homeworlds of many posthuman cultures.

The concept of a destination being "too far in the future" was meaningless to the Houses; their travel past the frontier was limited only because so many other time-aware cultures were active in the later universe. Since they preferred to believe themselves to be masters of causality and overseers of the whole continuum, members of the Houses rarely ventured into the frontier. (PROSE: The Book of the War) The Tenth Doctor said that Time Lords never went as far as the year 100,000,000,000,000, though hid there during the Last Great Time War. (TV: Utopia) The Eighth Doctor needed to force his TARDIS to visit Endpoint in an attempt to see how far in the future he could go; it needed to recalibrate before it could dematerialise again. (PROSE: Hope)

Faction Paradox had no difficulty crossing the frontier and voyaging into the depths of the posthuman period, where they had links with underworld and even terrorist cabals; though the Houses accused them of conspiring with posthumans who scavenged wrecked Homeworld technology, the Faction instead voyaged past the frontier just for the satisfaction of doing something the Houses had made taboo.

During the War, the enemy patrolled the frontier and the areas beyond, suggesting that enemy forces may have been in full operation beyond the frontier. Homeworld timeships were frequently repelled from this region of the Spiral Politic and, more disturbingly, as many as five were destroyed or captured along with their occupants. Compassion found the crumpled remains of the 103-form timeship Percival on the frontier, abandoned on a barren rock on the edge of posthuman history. Percival's pilot was still alive despite having been stripped of all his major organs, though he died after a few hours on the Homeworld. Carmen Yeh told of this event and Compassion's subsequent confrontation of the War King in her fictionalised memorial Fantastical Travels in an Infinite Universe.

The Uptime Gate to the City of the Saved was located in the universe almost exactly on the frontier in time. The Book of the War suggested that this might imply detente or even alliance between the City and the enemy forces patrolling the frontier.

Zo la Domini was one of the markers of the frontier in time; after a Violent Unknown Event occurred there, Thessalia chose another location on the frontier (PROSE: The Book of the War) to unleash the babel. (PROSE: Newtons Sleep)

Simia KK98 was on the edge of the Great Houses' noosphere.

When an expeditionary cohort of the Seventh Wave was cut off from Homeworld contact close to the frontier with only an outmoded 89-form timeship, Quintessence Officer Hierarchio predicted their chances of return to be minimal and suggested that they settle on one of the still-accessible worlds. There, the troops visited the Anvil Stars region and observed the birth of new universes and the creation of Leviathans. (PROSE: The Book of the War)