Board Thread:General Discussion/@comment-27907368-20160514064034/@comment-27620479-20160516203414

I don't think it is specified anywhere, that Toriel or Asgore have been on the surface. Also, the prophecy predates written history, which may expand the possible timeline way before 201X, Chara's arrival, given that monsters have left written instructions on the puzzles in the Ruins, their first home in the underworld. The caves, in which they live, were already there before the humans, likely in the middle ages, banished them there. There are a long possible list of unmentioned and unappearing humans and boss monsters, who could have been there in what is centuries before Chara or Asriel. The two of them are logical candidates, because they are in the game, and the description of the prophecy may fit them.

Gerson, on the other hand, tells that the angel will descend from above, and Asriel and Chara have returned through what seems to be a flat hillside (the place in the pacifist epilogue), so they are just as likely to have climbed up, and then went straight, instead of falling down through the hole on the other side.

We don't even know if the prophecy is true, and if it isn't, Chara and Asriel become less likely candidates for it.