One of those who is no stranger to chaos in the personification of darkness (6)

I believe the answer is:

erebus

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'darkness' is the definition.
(personification of darkness in Greek myth)

I don't understand the rest of the clue.

(Other definitions for erebus that I've seen before include "Antarctic volcano; region between earth and Hades" , "Dark and gloomy cavern between earth and Hades." , "God of darkness - cavern on the way to Hades - active volcano in Antarctica" , "It's hellish dark" , "The abode of the dead" .)

I've seen this clue in the Irish Times.

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