Corvax Fen was a swamp-like and forested region situated on the planet of Mustafar.
Decades prior to later events, the battle on Mustafar saw a descendant of Lady Corvax obliterate the Bright Star, which led to the formation of Corvax Fen. The energy released from the Bright Star's destruction permeated the barren soil of the planet, eventually giving rise to the forest. At some point, the astromech droid R5-Z0MB, with a striking resemblance to an organic zombie, began to roam the swamps of Corvax Fen.
By 35 ABY, the Corvax Fen had become the adopted homeland of a cult known as the Alazmec of Winsit. This group dedicated themselves to revitalizing Mustafar and safeguarding the remains of Darth Vader's castle. The Alazmec cultists held the belief that the fen's soil was fertile due to being saturated with Lady Corvax's tears. With a focus on protecting and rejuvenating the grove, the cultists began cultivating a forest of irontrees. In 35 ABY, Kylo Ren, the Supreme Leader of the First Order, arrived in Corvax Fen with a contingent of stormtroopers during his search to find the origin of Palpatine's broadcast. He subsequently massacred the Alazmec cultists and seized a Sith wayfinder that had once belonged to Vader.