Larian Studios Forums Divinity 2 - Ego Draconis (English) Help/Tips/Tricks [Help!!] Question about the Necromancer

So I'm reading about how to kill Amdusias and I keep seeing "Sick your creature on him." I think I know what cave the necromancer is in, but when I go there he is gone. I didn't go there for a long time because the room he is in, in that cave had a locked door so I never thought anything of it, or at least until after I got that creature skull and saw that I could summon a creature. I could really use the help with killing this guy so getting a creature would be great. But I was wondering where is the necromancer now? Did I go back too late? Other posts I see are extremely vague and don't help that much. Any help would be appreciated.