One could argue this war began when Lavina first appeared. During the first expedition of Janesborough, they stumbled upon a temple of Eclipse magic in the far north. There they met Logan, a powerful mage, and were then surprised by Lavina's sudden appearance. She released the explorers, but not after taking a life.
Or, perhaps, the war started when Lavina began reviving her siblings. In the midst of the conflict between Janesborough and Lubeck, Lavina obtained an enchanted Mirror with power over souls. This she used to resurrect her sister, Calamity.
At this point, Lavina was considered a certain enemy of all. This view changed, however, when Janesborough found itself besieged by a host of the Undead. Just as the army had breached Janesborough's walls, Lavina arrived, and, for no apparent reason, single-handedly forced the creatures into a full retreat. After this, opinions of Lavina rose. This is crucial, because this resulted in many citizens of Janesborough and the majority of Vargad allying themselves with Lavina.
Unlike Lavina, who'd been recruiting mortal allies for much time, Dara only sent Locke to gain followers just before the final battle began. Only some members of Janesborough joined.
Finally, Lavina's third sister was revived. With this, Lavina was prepared, and shortly after the battle began Dara and Lavina began. Dara sent the first shot in the war, attacking Janesborough. Lavina responded with fire sent at Halith, and soon both sides fired all over the world, targeting anything and everything that may help their ally. Vargad, Janesborough, and Halith were completely wiped out. Few escaped Janesborough alive, aided by Halith ships.
Obeying the directions of the Northerners, the refugees sailed to the far tundra. There they witnessed Dara and Locke's final defeat, the Sisterhood's betrayal of Lavina, and a black spire rising from the sea, emitting an eerie black mist.
They made berth and, attacked by Stalkers and Giants, hiked to the Dwarven doors. There they learned only a blood sacrifice could open the way into the ancient city. Four volunteered, and the doors swung open. They were met by a small army of Dwarves, who led the group, under armed escort, into Rohadren.