Dragon Quest IV: Chapters of the Chosen Cheats :
PsAro the Manslayer
In order to unlock him, you must beat chapters 1-5. Then, you must go to the hidden dungeon(I won't say where) and beat Fu yong and Chow mein. Jump into the volcano afterwards. Then, go to Rose's grave. Use the item you have recieved to revive her. Take her to Psaro and he will calm down. He will join your team and you must now defeat/kill Aamon.