Aamon

"Yes, it was I! I, Aamon, who effected Rose's death and ensured your demise!"

- Aamon to Psaro "Can you control your hatred!? Your loathing? But what of self-loathing? What shame could be greater than joining forces with the humans!?"

- Aamon to Psaro

Aamon is an evil demonic priest who works for Psaro in Dragon Quest IV. While seemingly his loyal servant, in the game's remakes he is revealed to be the true antagonist of the story and the orchestrator behind all the tragic events that led Psaro to his corruption; most notably the death of his lover, Rose.

He committed these horrendous acts in order to increase Psaro's hatred for humanity while at the same time getting rid of Rose as she was softening him and convincing him that humans weren't so bad, this forced him to acquire and use the "Secret of Evolution" to transform and get rid of all humans and once his transformation proved safe and successful, Aamon used the secret on himself in order to turn into a demonic god-like entity.

History
Aamon first encounters the heroes in one of the towers that generate Psaro's barrier along with Pruslas, Barbatos and Rashaverak. He taunts them and tells them that they stand no chance. He fights with three Drooling ghouls. Despite his powerful magic he is seemingly defeated and disappears.

If the heroes return to Psaro's old castle with the reformed Psaro by their side, they will discover that Aamon did indeed survive and was slowly getting ready to act out his own plans but showed displeasure that Psaro failed to destroy humanity as he desired, so he instead uses the Secret of Evolution on himself to become a horrifying demonic deity similar to Psaro's final demon form. In this form, his strength proves to even dwarf Psaro's and possesses magic far greater than before. However with Psaro and the heroes' combined strength they are able to overpower him and destroy him once and for all.

Other appearances
Aamon (his original priest form) is an obtainable monster in Dragon Quest Monsters Joker 2: Professional, but that version of DQMJ2 was not released outside of Japan.