There, he met Tartarus, and made a deal with him.
Nyxtharion would help Tartarus maintain the nightmare world – the hell for evil – and when Tartarus would die, he would give Nyxtharion the blood of Hades he had.
Since Hades himself was an ancient dragon, it would help Nyxtharion possibly evolve from Elder Dragon to Ancient Dragon.
The next events were history. Nyxtharion became a Great Disaster, was defeated by Ezra Williams, and now he was nearly erased by Thanatos.
For someone whose past was an epic in itself, Nyxtharion's end was pitiful.
He died pitifully, no longer remembering his goals and ambitions.
All he was now was a broken puppet.
[Modification for question 'How do I increase my World Energy Generation rate with least amount of effort?' has been completed.]
Thanatos looked at the empty area where Nyxtharion #1 had been until a few moments ago.
Power surged through him, and countless notifications appeared before his eyes.