Overview
The Eternal War pits Rahmavir against the Oracles of Eternity over the source beneath Zarephon. The Eternal War also targets the Plains of Eternity because the Plains spread outward from the source and force Rahmavir border cities to be abandoned.
The Eternal War centers on Zarephon and the Oracles. Rahmavir wants the source to stop the Plains from spreading and to gain access to origin magic. The Oracles guard the source, keep its flow free, and refuse to let Rahmavir or any outside power control it.
Cause
Rahmavir, Myrravel, and the Oracles try diplomacy before Rahmavir attacks the Oracles over the source. The Oracles refuse to control the source's flow or hand control to outsiders. Rahmavir attacks after the diplomacy fails, and its army disappears or is erased by Oracle power.
After that defeat, the Eternal War continues through broken diplomacy, raids, and repeated attempts to test Oracle defenses. Rahmavir spends the years between raids against Oracle defenses raising mages who can survive the Plains' volatile essence and eventually reach Zarephon.
Course
Myrravel fights on a related front after the Plains consume its own lands. Myrravel soldiers later admit that their side sought the source and wanted the Oracles dead because the Oracles refused to control the Plains.
Malverand enters the Eternal War after Rahmavir asks for troops against the Plains of Eternity. Thamrielle operates from Rahmavir, Phariel commands Malverand troops there until Abraxas kills him, and Thamrielle later reaches Zarephon and takes a planted essence core she believes is the source.
Alistair later joins a Rahmavir attack while Myrravel pressures the Plains from another side. Rahmavir aims for a three-pronged assault on Zarephon. Rahmavir's three-pronged assault on Zarephon fails under the Plains' distortions and the Oracles' defenses.
Fall of Zarephon
The Eternal War ends when Raphael's faction joins Rahmavir's final push against the Oracles at Zarephon. Raphael leads Alistair's embedded agents and Rahmavir's strongest mages into the Plains.
The original Abraxas is absent from Zarephon during Raphael's final attack on Zarephon. The Oracles defending the city fall, and Rahmavir captures Zarephon mostly intact. Rahmavir then establishes a direct route to the city and begins integrating former Oracles into its ranks.
Aftermath
Rahmavir gains access to Zarephon, Oracle records, origin-magic teaching, the source cave, and the lake beneath the mountain. The first attempt to descend to the source crushes a man under the lake's gravity. The spellwork in the cave and city also resists removal, so Raphael forbids careless interference with the cave.
The victory ends the Rahmavir-Oracles war, but it does not close the source. The breach remains active, and Rahmavir continues studying origin magic, the murals, and the source after Zarephon's capture.