create a powerfull virus ,somekind of zombie virus,add 'any liveing creature killed by this virus souls will instantly be transfered to the system' throw the virus in a low magic and low tech world and profit and thanks for the chapter
Another funny idea would be if he goes to Marvel or DC and doesn't fight anybody but once again just sacrifices the entirety of the Marvel Universe to the Warhammer gods
Let's be honest blacklight virus and then sacrifice a world to the chaos gods of Warhammer also I think you should kind of start from fresh even if they are slower to release but an item he should prepare is something that keeps his mind free of the chaos Gods even if they give him their power