You know, the exact words of The Prophecy in Undertale are kind of interesting, when you think about them. “An angel who has seen the surface will come, and the underground will go empty.” Closely associated with this prophecy is the ‘Delta Rune,’ which has been adopted as a symbol of the royal family. As a bonus, the ‘Delta rune’ itself is an anagram for the name of the game, ‘Undertale,’ so it’s clearly important to our story. Perhaps it’s even THE most important thing to our story.

On paper, the Kill-All run actually meets all the listed criteria for this. Chara, Frisk and Asriel have all seen the surface, and they are all instrumental to helping you get to the point. Asriel helps you solve puzzles, and may have even stopped reports of this tragedy from reaching Asgore until too late. And at the absolute, Chara destroys all of existence, all of time, which certainly qualifies as emptying the Underground, right? Except, the imagery of the delta rune itself doesn’t really seem to come into it. Look at the thing.

The ‘angel’ has great big white wings, doesn’t it? And, at the bottom, what are those three triangles meant to represent? It’s kinda hard to figure out. Doesn’t seem to have to do with anything that happens in the kill all, actually. However, its meaning in the pacifist is a little more transparent. The angel clearly refers to Asriel in his God of Hyperdeath form, right? And when he absorbs all the monsters’ souls, there’s nobody LEFT in the Underground right? So the prophecy is—

… So he didn’t absorb ALL the souls, did he? There was still some left behind? Well, no matter, right? After that, everyone leaves the underground? No, wait, let me help you figure that one out; “Don’t worry about me. Someone has to take care of these flowers.”

Interesting, isn’t it? Nothing really seems to fulfill the prophecy properly.

Even if Asriel, soulless, doesn’t ‘count’ as a person, then a throwaway line by gyftroot in the pacifist ending reveals that he intends on staying in the Underground after everyone has left in order to get some peace and quiet. So, in the pacifist ending, the letter of the prophecy is never fulfilled. In the Kill-All ending, the imagery of the Delta rune doesn’t make any sense.

There are three endings to Undertale. Neutral, pacifist, and kill-all. Delta is the Greek letter for the number ‘four.’

Maybe we’re not as finished with Undertale as we thought we were. Food for thought.