A year prior to the events of Eternal Diva, Oswald Whistler built the Detragon to contain Melina's memories after she had died, hoping that one day he could find an appropriate host. Anyone chosen as a candidate would be connected to the machine via a helmet wired to the machine and have Melina's memories pumped into their brain.
Everyone that was used as a candidate ended up resisting the memories of Melina, the only person who willingly allowed the memories into her mind was Janice Quatlane. However, Oswald didn't know that the transfer was successful. He became desperate, knowing that the Detragon could only hold her memories for a cetain time period. He therefore used the ruse of the competitin of Eternal Life to gain another candidate to hold Melina's memories.
Jean Descole agreed to aid him with his search. However, unknown to Oswald, Descole was double-crossing him to fulfill an ambition of his own; to raise Ambrosia from the sea. After Layton thwarted both of their plans, Descole revealed that he had altered the Detragon to transform into a much bigger and more deadly machine - the Detra-gigant. It was destroyed after the fight between Layton and Descole when Descole accidentally destroyed the panel controlling it. The machine went out of control and fell off the edge of the cliff into the sea below, impaling itself on the pipes that were in the ruins of Ambrosia.