Since he became aware of certain historical information regarding the Glorious Era on the Mycroft Continent, Joshua had his doubts.
A thousand years ago, in the latter stages of that era, the Mycroft Continent had opened dimensional passageways leading to the abyssal planes out of pride. Countless demons and curious Evil Gods came, igniting a war against the civilization that was at its peak—and after the war, it was the Sage who led the gods and all life to triumph against all foes after paying a great price.
Most gods—virtually all main deities—had died in battle or were permanently maimed. They were only able to leave legacy marks and their last ounce of divine power so that their own soul would turn into Divine Dungeon Shrouds tethered to the Infinite Horizon.
And yet the Sage was clearly not that heavily injured. He even had the power to divert part of his powers to create the Fourth Legacy in search of a successor.