The Cagebreaker was a meteor that impacted a mountain in the eastern Cage, near the mouth of the Lesser Onyx River, in Y9303*. On impact it shattered the mountain peak, causing an avalanche of debris that swept through the the neighboring valley and a dust cloud that choked out the area for days before finally settling in a heavy layer.
Despite the scale of the destruction, loss of life from the Cagebreaker was minimal owing to the divination of the Ether Council, which warned of its arrival several days in advance, allowing the pastoralists of the valley ample time to gather their animals and escape. Many credit this event with establishing the legitimacy of the Ether Council and ending dissent against their rule.
Ultimately the impact also revealed massive amounts of onyx. The mines established to exploit these have brought immense wealth to Rovakhit.