Character from Undertale / Deltarune by Toby Fox
The Royal Scientist who fell into his own creation and was shattered across time and space — a mystery that spans both games and may be pulling every string.
Gaster is Undertale's deepest mystery and Deltarune's biggest shadow. He was the Royal Scientist before Alphys — the one who built the CORE, the Underground's power source. His followers describe his fate in conflicting accounts: he fell into his creation, his experiments went wrong, he was shattered across time and space. All of these may be true simultaneously. His connections to Sans are the strongest evidence of his existence: Sans owns a workshop with blueprints and a broken machine. Sans's signature attack is called 'Gaster Blaster.' The font Gaster speaks in (Wingdings) mirrors Sans and Papyrus being named after fonts. Entry Number Seventeen — hidden in the game's code — ends with 'WHAT DO YOU TWO THINK,' possibly addressed to Sans and Alphys. In Deltarune, his influence is everywhere. The game's introduction is narrated by a mysterious figure creating a vessel. The phone calls that drove Spamton mad may have been from Gaster. The 'strange someone' who enlightened Jevil may be Gaster. The number 666 appears throughout his code entries. He is never directly encountered. He may be the most important character in both games. The game refuses to confirm or deny this.
No officially confirmed appearance. The 'Mystery Man' found in a hidden room is a black-and-white figure with a cracked, distorted face — smooth, featureless, with two dark holes where eyes should be. He vanishes when approached. He has no collision physics. He may not be entirely real.
Also known as: W.D. Gaster, The Man Who Speaks in Hands, Mystery Man