For the official spin-off/sequel of Undertale created by Toby Fox, see deltarune.

The Delta Rune is the emblem of the Dreemurr royal family of boss monsters from the smash-hit indie game "Undertale, developed by Toby Fox. It shows an orb between two wings and three triangles beneath it, with the middle triangle inverted.

"There is a prophecy. The Angel... The One Who Has Seen The Surface... They will return. And the underground will go empty."

— Ancient Glyphs in Waterfall

The Delta Rune is said to symbolize a prophecy that predates written history, although the original meaning has been lost in time. The only thing that can be said with certainty is that the triangles below symbolize the monsters of the Underground; although many believe the winged circle symbolizes an "angel." The prophecy narrates of an "angel" who has seen the surface, who will return to the Underground and bring the monsters freedom.

This prophecy has two interpretations: one where the "angel" destroys the barrier and brings freedom to the monsters (represented in-game by the True Pacifist ending), and one where it is an "Angel of Death" that kills everyone in the Underground (represented by the Genocide ending).^[1]