The Titans are bound in Tartarus, or they were....

Tartarus was a prison and holding pen for creatures distasteful to the reigning gods. When Oranos ruled the cosmos he locked many of his ill-begotten children in the depths of Tartarus. When the Olympians rose to power they threw the deposed Titans into Tartarus and bound them there with gates wrought of adamantine. The Titans spent millennia trying to find ways out of their prison, often enlisting mortals to free them. 

This gate is a breach in that deep, dark prison and the Titans await below. Task builders onto the Gate to dig away the rocks and rubble. When all the debris is clear, a Titan will emerge.