Plot point.

Spherical artifact, like a shiny obsidian ball. A great prize that much must be sacrificed in terms of quest, kin and/or comrades to obtain. It is the desperate last hope, the deus ex machina.

When it is obtained, there is one final sacrifice.

Two people, one man and one woman must hold the artifact together, and merge into it.

They do not die, but shrink into a minature adam and eve on the surface of the artifact which is now their world. They break away from our time continuum and live hyper accelerated existences.

They will be dead from old age a minute after they have gone into the sphere, but they will procreate, and their descendants will go forth and multiply, and the obsidian sphere will flourish like a mini-planet before the broken hearted protagonist. Nations, civilizations will rise and fall in moments.

Evemtually, guided by the destiny imbued in the sphere, its inhabitants will solve a mystery on construct an artifact required by the protagonist, and the sphere so spent will cease to be habitable, and extinction follows.

And there is an epilogue for the people of that strange planet.