Hellhound aka Beast of Darkness are manifestation of all evil, rage and grief from Guts' inner self after Griffith's betrayal and Eclipse event. From both events, Guts suffers dissosiative personality disorder where Hellhound inside him borns, and took over his mind for the first time as Guts wore the Berserker Armor for the first time.
Hellhound is aggressive, cold, cruel, and has an unsatiable battle lust. It also shown a bit manipulative, as it urges Guts to closer with his comrades so should he suffers their loss, it can took over his mind.
Hellhound bears some similarities with with Lord Vile;
- Both are manifestation of rage, hatred, and grief inside protagonist (Lord Vile for Skulduggery and Hellhound for Guts)
- Both are created as alternate personality of both heroes by respective main antagonist unintentionally (Hellhound by Griffith with the Eclipse and sacrificing the Band of Hawk and Lord Vile by Nefarian Serpine by slaughter Skulduggery's entire family).
- Finally, both tries to take over the protagonist's mind should they wear their black armor (Hellhound tries to take over Guts' mind as long as he wear Berserker Armor while Lord Vile mainly took control of Skulduggery should he wear his armor again).