OverLord

The Boss of Level 5

Lore

Is confirmed as at least one of the prior visitors. It's known that only two made it. It looks similar to D-13.

And from what's known, the page has the simple quote "I Failed". Which implies that it reached the Power Eternal but didn't use it to try and restore the world. But instead control what already exists. Perhaps to make it better. But was unable to.