My journey through Athena on the NES nears its end! We've arrived at the World of Labyrinth, which I've only seen a couple times before; it's either the second-to-last level in the game, or the third-to-last.
So that's the solution to how, when I played Athena as a kid, I was able to see the World of Hell once, and the World of Labyrinth a couple times, and have no idea why the game seemed to be so uncertain about the sequence of the stages. Mysterious!
It turns out there is no Boss in the World of Labyrinth, so the only way to escape is to use what in other Worlds was just optional: we need to find a Lamp in order to safely make it past the last room.