Skeleton
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About
The body of a character who permanently died will decay into a Skeleton after 24 hours.
Permanent death is either the result of Disease, Murder (either by players or darkness creatures), or getting KO during a Blood Moon. On expedition servers it's also possible to be permanently killed from Cannon shots.
Descendants of a deceased character can bury these remains to be able to regain lost proficiencies. See the Burial Rights skill to learn more about this.