In Dragon Quest II, the corrupt cleric Hargon and the God of Destruction Malroth were defeated by the ancestors of the Hero, and peace was brought back to the world. However, a religious group that wants to pick up where Hargon left off has arrived and brought a new terror.
In the original Dragon Quest II, Hargon is initially established as the main antagonist and is for the most part of the game. Upon defeating him, he uses his last breath to offer himself to Malroth as a sacrifice and dies. This summons the God of Destruction Malroth, which ends up being the final battle of the game.
After Hargon was defeated, peace was disturbed by the Hargon Order, that has been bringing destruction to various towns and castles across the lands and with most of it in ruins, the remainder of humanity is scarce.
The Order’s objective is to destroy the world, and the Builder that has the power of creation is a bother to the group, so they decided to capture the protagonist and throw him/her into jail.