Nergaal is an ancient Warlord who can be found in his tomb during the quest No Rest for the Wicked. He appears to guard the recipe for 'An elixir that would give him unnatural lust and sexual endurance.' which he used in life to satisfy his harem that he had hand-selected out of his conquests.
Nergaal only has two abilities;
Between the summons & slow circle, ranged attacks can be quite effective in taking Nergaal down while you kite the Cursed around the room.