Undertale, the Steam RPG hit where you don't have to kill anyone, is loaded with secrets. Dedicated players have unearthed every last one... well, except for the last one.
(Big Undertale spoilers ahead.)
I addressed Undertale's last big mystery a bit in my piece on the unique ways the game weaves its web of secrets, but things have gotten a lot more complicated since then. This is a mystery that sure seems like it doesn't want to be solved — at least, not conclusively. Players have had to dig through countless game files and arrange volumes of evidence in an attempt to answer one final question:
Who is W.D. Gaster?
If you play Undertale normally, you won't encounter any direct references to Gaster. Players have found what they think to be hints at his existence in-game — most notoriously from the hooded figure who captains Undertale's fast travel boat and also in skeleton character Sans' weapon, the Gasterblaster, when you fight him in a so-called "genocide run" of the game — but they have mostly unearthed information about Gaster by datamining the game's code.
Nobody's entirely sure who Gaster is, but dialogue from a handful of creepy grey NPCs you can only encounter by plucking their areas of the game — or "rooms" — from the game's code seems to suggest that he was some kind of skeleton scientist conducting experiments involving space and time. It makes sense he'd be studying those forces, given that the story of Undertale came about due to characters — the player included — with time-warping abilities called "save" and "load." (Yes, that's actually part of Undertale's plot. It's super meta, but not in, like, a cloying way.) In the process, apparently Gaster created a legendary invention, The Core, only to fall into "his creation" and die.
Except maybe he's not dead at all. One of the grey NPCs tells the story like this:
"I understand why Asgore [the king of Undertale's monster world] waited so long to hire a new Royal Scientist. The previous one... Dr. Gaster. His brilliance was irreplaceable. However, his life was cut short. One day, his experiments went wrong and... well, I needn't gossip. After all, it's rude to talk about someone who's listening."
This has led players to speculate that Gaster's very being was spread — like a painfully small dollop of butter on toast — across space and time in infinitesimally small quantities. Gaster is nowhere. Gaster is everywhere.
Things get stranger from there. Players have uncovered a secret sound test room that includes a track called "Gaster's theme." It sounds like the music that would play in a slasher flick the first time you get a good look at the villain's gnarled, sickly features. Also, if you try to name your character "Gaster" when you start the game, it just boots you back to the intro video, forcing you to start over.
The rest is downright spooky. For instance, players discovered that if they change their room number in two keys files, a set of wingdings (yes, the bizarre symbolic font you discovered as a kid in Microsoft Word and spent 15 whole minutes cackling at; you never thought about it again until now) appears. Translated out of batshit, they read:
ENTRY NUMBER SEVENTEEN
DARK DARKER YET DARKER
THE DARKNESS KEEPS GROWING
THE SHADOWS CUTTING DEEPER
PHOTON READINGS NEGATIVE
THIS NEXT EXPERIMENT
WHAT DO YOU TWO THINK?
From this, we get a couple things: 1) Entry 17 is normally a missing entry in the "True Lab," a location in Undertale's pacifist ending where bumbling scientist Alphys goes to try and set things right. Odds are, Gaster made it back when the lab was his. 2) The message is in wingdings, a choice that reeks of strangeness for strangeness' sake until you consider Gaster's initials: W.D. Players have taken to speculating that Gaster's full name is Wing Ding Gaster, and he speaks predominately in wingdings. Thus, many have concluded, Gaster must be a skeleton like Sans and Papyrus — two of Undertale's most endearing characters — who also "speak" in the fonts they're named after.
Gaster's connection to Sans, especially, seems strong. Some even think they might be brothers. If you do some save/load trickery before the big end-of-game encounter with Sans in a pacifist playthrough of Undertale, Sans will grant you access to his secret workshop, which contains a weird machine. There are also blueprints written in strange "symbols. Or maybe it's just the handwriting." Strange symbols like... wingdings? Some have speculated that the machine is one of Gaster's creations, an idea that gains credence when you consider why Sans gave you a peek behind the curtain in the first place: he knew that you manipulated space and time, because he can do it too. This is further backed up by one early game character, Doggo, noting that he's not a fan of Sans because Sans can travel without moving. And of course, as I mentioned earlier, there's Sans' weapon in genocide runs, the Gasterblaster.
Last but certainly not least, players have uncovered what they believe to be a couple encounters with Gaster himself — or Gaster speaking through other characters. These are accessed by capitalising your "Fun" value in the game's files and messing with associated numbers.
One is a grey monster child who asks if you've "ever thought about a world where everything is exactly the same, except you don't exist." Some players think it's a fragment of Gaster speaking on what it's like to be scattered across space and time.
Then there's what many speculate to be an encounter with Gaster himself. In short, a mysterious grey door spawns, and inside there's this spooky-arse phantom skele-man:
He disappears when you approach, as though it's nearly impossible for him to remain in a single spot — like his very essence is held together by nothing but the final vestiges of his will.
You might have noticed a trend here: speculation. Yes, players have painstakingly scoured Undertale for every scrap of evidence they can find, but in piecing it together, they have made less of an artful collage and more of a macaroni painting. It could, in other words, all be bullshit — stuff Undertale creator Toby Fox scrapped, never intending for it to be found. A storyline cobbled together from evidence that's circumstantial at best, a skeleton made of mismatched bones.
Recently, however, Fox directly acknowledged some of this stuff in an in-character Tumblr post. As Sans, he wrote about real-life concerns that Undertale contains some prejudiced elements. It was an earnest, interesting post, but it also contained this nugget:
"just remember: there's a difference between protecting your friends and destroying someone for your own justice. for honesty's sake, investigate the truth for yourself, then ask: how is this going to help people?"
"besides, it's rude to talk about people that are listening, right? not everyone is as tough as my brother."
"It's rude to talk about people that are listening." Almost a direct quote of what that grey NPC said. And while you might at first think Sans is referring to his brother Papyrus, it could just as easily — given the preceding line and Papyrus' lack of, you know, omniscience — be Gaster.
Fox keeps up with Undertale's community. He almost certainly knew exactly what he was doing here. Given how deep many other Undertale secrets run, it's possible that he intended for some of this to be found. However, Fox has also said future updates for Undertale likely won't include any new content (just bug fixes), so it's unlikely that the game will directly explore any of this.
But that hasn't stopped players' imaginations from running wild. So they continue to datamine, uncover clues, and push toward a better understanding of Undertale's final mystery — sometimes even in the face of adversity. The big collaborative Google doc many players were using for a while, for example, got vandalised beyond the point of saving by Internet miscreants. So they packed up their info and moved elsewhere — to a page on Steam, Undertale's official forums, and a datamining-focused subreddit, among other places. Players post and speculate daily. The effort is, without a doubt, ongoing.
Recently, an almost professional-looking Gaster website popped up, further stoking the flames of fans' obsession. It's almost certainly fake, but people desperately want to believe it's real. They have scoured Undertale — picked over everything time and time again, ravenously torn through its viscera — but they still don't know the full story. There are so many questions left, so many gaping holes in Gaster's tale. They want to know more about Gaster and the true nature of Undertale's world. They need to. But maybe they never well. And perhaps that's for the best. Good mysteries end. Great mysteries linger.