The Eighth Interval is the period of time in Pernese history that began at the end of the Eighth Pass and ended at the beginning of the Ninth Pass. It spanned the Turns 2058AL through 2508AL. It is also known as the Second Long Interval.
The Eighth Interval was the second time in Pern's known history that did not see a 50 year Pass following 200 years of Thread-free skies. Instead, the Interval extended for approximately 200 years following the expected 200 year interval period. As a result, belief in Thread diminished and the dragonriders were seen as useless and just using resources.
The early parts of the Eighth Interval was marked by the sudden disappearance all the Weyrs, barring Benden Weyr, who remained unaware of the reasons for this disappearance. The apparent abandonment helped to fuel the rumors that Thread was not returning and that the Weyrs were unnecessary. Within Benden Weyr, a succession of events led to the Weyr being isolated, with the dragon species in danger of extinction due to the presence of only one queen at any time.
The Eighth Interval also saw expanded rights for the Holds and Crafts, which had been totally subservient to the Weyrs during the previous pass. However, it also saw the loss of older technologies and comforts, such as flamethrowers. As the lack of Thread allowed for expansion of forests and greenery, wood became increasingly more common as a building material. As time went on, teaching of Thread and dragon-related subjects was restricted by more hostile Holders.
The later portions of the Interval were dominated by the rise of Fax, who conquered multiple Holds. His thirst for conquest led to the murder of all of the Ruathan bloodline barring Lessa, who was forced into hiding. Fax's downfall would come in the latter portions of the Interval, when he was killed in a duel with F'lar when Fax refused to renounce Ruatha in favor of his son.
As the Ninth Pass began, it was eventually revealed that the five missing Weyrs had in fact, left to travel to the Ninth Pass to assist in the fight against Thread. The discovery of AIVAS during the Ninth Pass also led to the discovery that both Long Intervals were caused by antimatter engine explosions that led to alterations in the Red Star's orbit, which were part of AIVAS's plan to eliminate Thread.