Yore

Yore is an extra boss from Dragon Quest IX. An imprisoned demon beneath Stornway Castle and the one responsible for the destruction of Brigadoom. He has a henchwoman named Morag.

Backstory
After the main events of the game are concluded, the Hero aids a group of people calling themselves the Brigadoom Brigade to make the ruined city inhabitable again and retrieve information of what could have caused its fall. Princess Simona, with the aid of the ghost of Princess Mona finds out that the former king of Stornway had sold Brigadoom, which the kingdom of Stornway maintained relationships, to Yore in charge of protection from the Gittish Empire and then imprisoned the demon in a coffin, fearful about what it might do. This upset Simona asked the hero to lead her to the coffin where the demon rested and when she gets there she reveals that she know wants her kingdom destroyed to compensate for Mona what the former king had done, her father the king tries and manages to knock some sense into her, but Yore is still awoken and wishess for revenge. It's up to the Hero to defeat this powerful foe.

According to the Bestiary this demon had already made a deal with the Gittish Empire to destroy Stornway as well, regardless of the outcome.