An UnderTale AU where W.D. Gaster is King before the war instead of Asgore Dreemurr. Gaster is not as naive a ruler and sees the war with humans coming years before it arrives. By then, he has already led monster kind to create a safe place for themselves underground. They willingly retreat there as soon as the war begins, sustaining minimal casualties, and gradually create an underground kingdom. Sans and Papyrus are the first and second princes. The barrier exists to keep humans out rather than monsters in. There will likely be crossovers in the future of the story.
20 parts