Total War: Warhammer III

Start with Xiao Ming's faction, as she both starts with one Gate under her control already and is closer to them. You should more or less get this playing normally. You will likely see enemies breaking through the Gates controlled by the AI relatively soon in your campaign. Simply defeat the enemies, resettle and rebuilt the Gates, keep them save by stationing additional troops there while it isn't completely rebuilt yet and you should have it before your third soul. You can even try to confederate or even outright conquer them yourself, but I found that that is unnecessary. But if you are just after the cheevo, it can be done quickly that way.