The legendary lost city of Doradus lies somewhere on Cybertron. It's said that this mythical realm is home to the Fountain of Energon, which grants whoever may find it with eternal power. It may possibly be protected by malevolent spirits.
The Decepticon Springload was obsessed with finding the lost city of Doradus, even to the point that he was oblivious to the fact that he was searching for it on the wrong planet. Bumblebee and Strongarm tricked him by impersonating spirits from Doradus so they could capture him. Springload was later sprung by Quillfire, who lied about knowing where Doradus was so that he could gain the Amphiboid's allegiance.
Some time later the Autobots located the Sphere of Doradus, which Springload (having stolen it from them) believed would allow the spirits to guide him to the lost city. The Sphere was destroyed before he could activate it, but as its remains were crushed in the scrapyard a holomap briefly flickered unseen, indicating the legend might well be true.