Just as the Dimensional Engine supplanted the fission reactor, the DTR will eventually replace the D-Engine. Once they iron out the little bugs.
The heroes have destroyed the minions, plunged through the catacombs and defeated the guardians. They slowly enter the chamber to find the dark mastermind behind the scheme. The mastermind has a request for them, however:
"You must destroy me. To destroy me is to rid the world of a great evil, that is to say, me. But before you can destroy me, you must understand what evil is, what evil must be, why evil must exist."