The Proving Massacre was an event involving Nora Brave candidates and Eclipse soldiers that occurred during the Proving of 3040. The massacre functioned as the catalyst for the events of Horizon Zero Dawn.
Events[]
Before the Massacre[]
The Proving is a long-standing Nora tradition, used as an initiation test for eighteen-year-old Nora who wish to become Braves.
Even without the looming disaster, the Proving of 3040 was notable for two reasons. First, a delegation from the neighboring Carja came to observe the Proving: this marked the first time any outlanders (let alone the Carja) had been permitted in the Embrace, and was a major step in Carja reparation efforts for the Red Raids. Among the delegation were two Oseram: the Vanguard Erend and scout Olin. Second, among the new candidates was the outcast Aloy, who had come to get answers as to her mother.
While many Nora were understandably upset about the Carja (especially with the Red Raids fresh in their minds), Erend kept tensions from boiling over. The eve of the Proving itself, Aloy noticed Olin wearing a Focus and approached him out of curiosity. Olin began acting strangely, but Aloy thought little of it at the time.
Unbeknownst to either the Nora or the Carja delegation, Olin was an Eclipse spy (albeit unwillingly), and HADES noticed Aloy through Olin's Focus: recognizing her as Elisabet Sobeck, it issued an order to Helis and the Eclipse to kill the girl. Under Helis' orders, they were to avoid contact with the Nora if possible, but kill any witnesses. A sizable number of Eclipse were already in the Sacred Lands at the time, presumably to excavate Faro machines, and set up camps in Devil's Grief, "cursed" ruins that the Nora would normally never check.
The Proving[]
The Brave candidates were to climb All-Mother Mountain, take pieces of Grazers through an obstacle course, and make it to the finish. Those who completed the challenge became Braves, and whoever made it to the finish line first would be granted a boon from High Matriarchs. Despite having difficulty with Bast over a Grazer piece, Aloy took another Grazer part, managed to cross a disused obstacle course, and achieved victory as the first Brave, which meant that she could speak to the Matriarchs about the issue of her mother.
The Massacre[]
With Aloy the victor, Bast tried to challenge her victory, but they were soon interrupted by a hail of arrows that struck down most of the other candidates and the proctor. Aloy, Bast, and Vala held off the attackers long enough for a few of the other Braves to escape. While a few did so, a cultist killed Bast and Vala with a machine gun. Aloy then managed to kill off most of the remaining cultists on her own.
Soon, Helis grabbed Aloy and, holding her by the neck over the edge of the cliff, attempted to kill her, but was interrupted by Rost. While Rost fought valiantly, he was ultimately bested and fatally stabbed by Helis.
The Eclipse then retreated, placing a bomb in the area to destroy any evidence. Rost's final act was to push Aloy off the ledge, saving her from the ensuing explosion.
Aftermath[]
The Nora were shocked and horrified at the scope of the massacre. The Carja delegation was escorted back to the Sundom immediately, and the Nora quickly prepared a War Party to retaliate against the killers. However, the Eclipse were well-prepared, and killed over half of the Braves in an ambush of corrupted machines. The Nora were left unable to patrol their borders, allowing for bandits to enter the Sacred Lands, and the presence of corrupted machines was brought to the attention of the wider world.
In summary, the aftermath of the massacre left the Nora on the verge of extinction, and was a massive stepping stone in Aloy's journey and discovery of her purpose in the world.