Karzahni

Even though in the main universe Karzahni is dead he does have some relevance to the EU, in the EU he was a former dark hunter that betrayed vishka and was then banished a realm that was named after him. The Karzahni Realm is basically the bionicle equivalent to hell matoran are tortured, dismantled, and turned into Karzahni's slaves.Eventually Toa Gali destroyed Karzahni's realm and later Karzahni himself got to get a taste of his own medicine and was dismantled by the Toa Kallu to be. Before being dismantled though he was trapped in the pit of mahri nui and battled with the toa mahri before being led back to his own realm were his torture began, Karzahni wears the kanohi olisi mask of alternate futures.
"KARZAHNI YOU HAVE BETRAYED ME AND THE DARK HUNTERS FOR THE FIRST AND LAST TIME"- vishka to karzahni after his betrayal