What a terrible and wonderful place the Gu World is... you could truly say that everything that happens to you, good or bad, is a result of your own strength, because even luck is strength here. There's no blaming others for the outcome, sadly.
All these Grotto Heavens presumably existed for very long. Because Heaven's Will looked after these Grotto Heavens, they all have dense Dao Marks. Fang Yuan's Dao Marks is going to get insane after this.