One of the RPG world's first Evil Plans (albeit a very simple one): when Garland reveals, at the end of the game, that he created a time loop by sending the Fiends 2000 years forward so they would send his body back 2000 years to allow him to transform into Chaos, and live forever.
Oh, he doesn't care overmuch about living forever, he wants to kill the Light Warriors forever. After they killed him as Garland, he hates them so much that killing them once just wouldn't be enough. He wants to spend eternity killing them over, and over, and over, and over, and over again.
The severing of said time loop by the Light Warriors may also count, if you actually care that much about the story to such a simple game.
The iconic bridge-crossing scene, which signals the real beginning of the game.
This game's very existence really. A dying company's employee makes one last ditch attempt at a good game. His only real standard: show up Dragon Quest. Instead of one character, choose any combination of four from six unique classes. Instead of less than a dozen boring spells, choose any 24 from at least 36 options. Instead of a handful of equipment, dozens of pieces that match the class options. It doesn't seem like much today, but back then, it was miles above what anyone thought a game could be. It saved a dying company and spawned one of the most famous video game series in the world.