From This official forum thread.

1500 years before present day: The Blood Storm invades, all but Regulos are imprisoned on Telara. Regulos's body is destroyed, and his spirit banished beyond a Ward erected by the Vigil to keep Telara safe from planar invasion.

500 years before present day: The Eth Empire, which rose in the wake of the Blood Storm Wars, falls. In its wake, the Mathosian Empire rises, ushering in a new age for the people of Telara.

25 years before present day: King Jostir dies, and his two sons, Aedraxis and Zareph, become tangled up in a Civil War over who will take the throne.

20 years before present day: Aedraxis uses the machines built for him by Orphiel Farwind to crack the Ward, unleashing the power of Regulos onto Telara in an event that would become known as the Shade. This triggers the beginning of the rifts. The heroes of the Guardians are returned for the first time to stop Aedraxis from completely handing Telara to Regulos. Many are taken up from Telara at that time to be presented with a vision from the Vigil. However, others, such as Cyril and Shyla, remain on Telara to defend it from the rifts.
At this time, Zareph and company go to Port Scion to be shielded within a great sourcestone barrier defending it against the planes. From there, they waged a long and bitter war against the rifts.

1 year before present day: An ancient Eth life factory is uncovered in Freemarch. Orphiel is able to get its Resurrection Forges functioning and returns Asha Catari from death. Unfortunately, hers would be the only soul returned with any sort of special powers, and hers were the product of a confrontation with Regulos and not true Ascension.

Shortly after that, Alsbeth betrays the people of Port Scion. She manipulates them into sending their forces out of the city, and then corrupts the city's magical defenses, allowing a massive death invasion in. The city falls and Zareph is lost, sacrificing himself to seal the evil inside.

Without Zareph to mediate, Orphiel and Cyril go their separate ways and take their followers with them. Thus you have the official division of the people of Telara into the Guardians and the Defiants.

Present Day - New ranks of Ascended Guardians return with a vision of Telara's destruction from the Vigil to guide their new crusade. All but simultaneously, Orphiel erects a Failsafe device, a temporal anchor by which Defiants might return if need be. As it is initiated, Ascended Defiants spill through from the future to tell of the world's forthcoming doom.

Defiant Future:

8 years after present day: Meridian is sacked by the Guardians. The surviving Defiants hole up within well fortified life factories to continue trying to solve the trouble of Ascension with machines.

14 years after present day: Orphiel disappears without a trace.

20 years after present day: Sylver Valis discovers the means to creating Ascended with machines. These new Defiants are sent back to try to avert the disaster they witness as they escape through the Failsafe to the past.

Yes, yes it does say "Meridian is sacked by the Guardians."