The Legend of Zelda series is infamous for its branching timeline, which involves the end of The Legend of Zelda: Ocarina of Time splitting off into three different versions of Hyrule. It turns out that the same thing happened with the original Dragon Quest game and it ties into the only way to get a game over in the entire series.
The story of Dragon Quest involves a nameless hero saving the land of Alefgard from the clutches of the wicked Dragonlord. When the player finally encounters the Dragonlord, they are given the choice to join him and rule over half of the world. If the player accepts the Dragonlord's offer, then they are put into a "long, long rest" and the game freezes. The only way to continue is to reset the game. The Dragonlord's offer is the only way to get a game over in the mainline Dragon Quest series, as later games will return the player to a nearby church if they fall in battle or will turn fatal character decisions into dreams.
The hero from Dragon Quest canonically refuses the Dragonlord's offer in the Erdrick trilogy, as Dragon Quest II: Luminaries of the Legendary Line takes place a century after the events of the original game and follows the hero's descendants.
The hero's non-canonical choice at the end of Dragon Quest would go on to form the basis for a different timeline, which spawned the Dragon Quest Builders series. It seems that the slumber that the Dragonlord put the hero into was only temporary and he would awaken in the future during a time when a new hero was rising.
In Dragon Quest Builders, it's revealed that the world the game takes place in is a ravaged version of Alefgard from the original Dragon Quest trilogy. The Dragonlord and his army were able to take over the land and they prevented any new structures from being built. The protagonist of the game has the power of the mythical builders of old and can rebuild the shattered cities and unite the remains of the population under a single banner.
The people who are familiar with the original Dragon Quest might think that the protagonist of the game is the same character as the hero who accepted the Dragonlord's offer, as they awaken in a tomb with no memory of their previous life. This theory is thrown out of the window during the last chapter of the game when a twisted version of the Dragon Quest hero appears as a boss.
The original Dragon Quest hero has become a mad tyrant known as the Fallen hero in Dragon Quest Builders. He resides in a small castle and believes himself to be the ruler of half of the world, as this was what the Dragonlord offered him at the end of Dragon Quest. It's up to the hero of Dragon Quest Builders to defeat the Fallen hero, before finally ending the threat of the Dragonlord once and for all.
The Dragon Quest series has always been about grinding for levels and gaining new equipment in order to overcome challenges, which is why there are few penalties for failure. The original Dragon Quest had the only true game over in the series, yet this moment was significant enough to be spun off into an alternate timeline that formed the basis for one of the most beloved games in the series.