Overview
The Brighthaven Civil War is the conflict between Isaac and Alistair Voss for control of Brighthaven. It begins after Alistair uses Vianna's resemblance to Pyrathalor and Brighthaven's distorted history as a pretext for consolidating power. The Brighthaven Civil War leaves Damian and Olivia dead, drives Vianna's family into exile, and ends when Isaac, Vianna, Pyrathalor, Kazimir, and Morozkayan mages overthrow Alistair in Radiance Prime.
Cause
Isaac trains Vianna at Radiance Prime Magic School until her name and fire-and-ice magic are known across Brighthaven. He does this to make it harder for Alistair to act quietly against her. Olivia and Damian understand the danger: Brighthaven's official history casts Pyrathalor as the destroyer of Radiance Prime, and Vianna gives Alistair a living target he can use to take fuller control of the Brighthaven Triarch.
Damian and Olivia confront Alistair first. The confrontation fails. Isaac brings Marcus, Vivian, Julian, and Vianna out of the city at night, Damian dies as explosions hit Brighthaven, and Brighthaven's construct defenses attack the family's boat. Isaac shields the escape long enough to get them away, then returns to Brighthaven to fight Alistair.
Course
Brighthaven splits into two factions under Isaac and Alistair, who fight for control. Garrik's scouts gather information from the island by ship at night, and Brighthaven uses ancient Malverand constructs with crude construction and effective combat performance during the Brighthaven Civil War.
Julian returns to lure Vianna back to Brighthaven with the false promise that the Brighthaven Civil War is over, Isaac is missing, and Alistair has changed. Alistair has given Julian a construct boat, crew, and orders to bring Vianna back. Pyrathalor rescues Vianna from the abduction attempt, and Vianna kills Julian before accepting a pact with Pyrathalor and going to Morozkaya.
Fall of Alistair
By the time Isaac reaches Vianna in Morozkaya, Brighthaven's government is near collapse. Damian and Olivia are dead, and Alistair rules alone from the Spire of Triumvirate with loyal followers still around him. Isaac asks Morozkaya for aid, and Pyrathalor sets the price for Morozkayan mages entering the Brighthaven Civil War: Brighthaven will later commit its fleet, trade access, and construct technology against Thalassai.
Isaac's allies deactivate the southern island defenses, allowing Isaac, Vianna, Pyrathalor, Kazimir, and a small Morozkayan force to enter Brighthaven. They reach the Spire of Triumvirate, isolate it from the city, and kill the defenders who resist. Vianna kills Alistair Voss, ending his Brighthaven regime. Voss is the Brighthaven-based ruler and division leader within Alistair's Network; the original Alistair survives into later events as Alice. Afterward, a new triarch governs Brighthaven and honors the deal with Morozkaya.