>>533591367
someone can probably answer in more detail but here's my stoner explanation
>orgres threatening to invade cathay
>cathay sorcers call down bigass warpstone meteor onto their homeland
>the crater of the meteor becomes corrupted by the hungry spirit of the ogres, turning into a massive hole with teeth and an insatiable appetite
>it in turn corrupts the ogre species, making them even more hungry but also able to call upon its power (somehow I don't know how on that part)
You can see the Great maw on the map, it's at the border between the Mountains of Mourn and the Warpstone desert.