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Umbra was an agro settlement on Caprica near the Thorn forest. It was destroyed in a sneak attack in 7322.

Chameleon was separated from his son Starbuck when the Cylons raided the settlement. This raid was apparently one of the "first raids on Caprica", according to Chameleon, and resulted in nearly three thousand children being orphaned (TOS: "The Man with Nine Lives").

In the separate continuity

As a competitor to Osiris' agro business ambitions, Umbra is offered to the Cylons as a target in their ongoing raids against various Colonies in 7322. After Osiris remotely deactivates the defense net, Cylons attack to devastating effect, despite the defense offered by the battlestar Rylon. Children and other survivors ventured into the nearby Forest of Thorns, amongst which a young amnesiac renamed Starbuck is rescued and fostered (Battlestar Galactica: Starbuck #1).

As a survivor of that raid, Starbuck later becomes a Colonial Warrior and recovers information acquired by McKintosh, an agro freighter captain formerly in Osiris' employ, regarding his former employer's complicity with the Cylons in the attack on Umbra—and other subsequent attacks spanning decades (Battlestar Galactica: Starbuck #4).