From Dark and Darker Wiki
If you enter the boss arena to spawn him, but leave before he's done forming and make sure he's not aggro'd to you, when you enter again he'll literally do nothing and you can kill him no issue.
From Dark and Darker Wiki
If you enter the boss arena to spawn him, but leave before he's done forming and make sure he's not aggro'd to you, when you enter again he'll literally do nothing and you can kill him no issue.