Take extreme caution. He will be surrounded by Dreadbeasts. Convince Dreadbeasts summoned by the towers around the room, and use these to defeat the boss. Try to trap Hellgorak with 7 dreadbeasts + the blocker. In a non pvp server you can have a druid stand close and constantly use Mass Healing to keep the Dreadbeasts alive, since you wont heal the demon. Failing this, have 8 knights surround it and use many, many, many runes to take it down (Each rune hits 1-3 damage).
Through the teleport in the Hives in the Inquisition Quest. He is the seventh and final boss.
Hellgorak is the last survivor of a demonic cabal which succumbed to the Ruthless Seven aeons ago. And Hellgorak is a survivor to the core. As the victory of the Ruthless Seven became more and more evident, he betrayed his allies and switched sides. Hellgorak decided it was better to serve under the Ruthless Seven than to die as a leader. Becoming a minion of the Ruthless Seven did not stop him from developing his evil plans. Slowly but steadily he climbed up in the ranks and used his new power and influence to improve himself. He called in favours, and killed those who possessed wisdom he needed.
Over time, his demonic plans yielded fruits. With the help of stolen secrets and enchantments, his dark body is covered with glowing ancient runes that protect him from most harm. He boasts about his invulnerability which actually was proven a lie by the agents of the inquisition. Still, he shakes off most damage with ease, and it would for sure take an insane amount of attackers to bring him down. It was prophesied that no man will beat him - right before he killed the oracle. Still, he fears the Ruthless Seven who defeated him and his allies in the past. Therefore, it is safe to say that, even though he is nearly invulnerable, Hellgorak is all but immortal. Creature Illusion is niet mogelijk.