Undertale Wiki
For information about another game by Toby Fox, see Deltarune on the Deltarune Wiki.

The Delta Rune is an emblem representing the Kingdom of Monsters.[1] It is an orb between two wings and three triangles beneath it, with the middle triangle inverted.

It is first seen on a Boss Monster's robe during Undertale's introduction scene, and secondly on Toriel's robe, foreshadowing her role in the story. The emblem or portions of it are depicted in various areas, armor, and occasionally, monsters visually resemble it.


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 predate written history. However, the original meaning has been lost in time. What is certain is the bottom triangles symbolize the monsters of the Underground. The winged circle is believed to represent the "angel," which is prophesized to be the one that has seen the Surface and will return one day to depopulate the underground.

This prophecy has two interpretations: one where the "angel" destroys the barrier and brings freedom to the monsters, and a more recent outlook on it, where it is an "Angel of Death" that kills everyone in the Underground, thus "freeing" them from the mortal realm.

Dialogue with Gerson

  • Oh yeah... The prophecy.
  • Legend has it, an 'angel' who has seen the surface will descend from above and bring us freedom.
  • Lately, the people have been taking a bleaker outlook...
  • Callin' that winged circle the 'Angel of Death'.
  • A harbinger of destruction, waitin' to 'free' us from this mortal realm...
  • In my opinion, when I see that little circle...
  • I jus' think it looks neat! Wahaha!



  • "Delta Rune" is an anagram of "Undertale."
  • "Delta Rune" may mean several things.
    • Delta is the fourth letter of the Greek alphabet, also known as "Δ". It reflects the triangles on the emblem.
    • "Rune" revolves around the meaning of magic, mystery, or spells, as the monsters mostly revolve around magic.
  • The prophecy states that when an angel appears, the underground will be empty. This hints at the two main routes to beat the game, in which Asriel Dreemurr may destroy the barrier and free all monsters, or the first human (by reincarnating through the protagonist) may kill all of the monsters and erase the world.
  • The Delta Rune bears a resemblance to the royal crest of The Legend of Zelda series, both with three triangles and a winged figure.


  1. "That's the Delta Rune, the emblem of our kingdom. The Kingdom... Of Monsters." - Gerson