The Dark Fountains are an important plot mechanic in Deltarune.
Dark Fountains are power sources that give a Dark World form. Ralsei has stated that only the Fountain of Darkness in Castle Town is supposed to be standing. However, King and Queen state that the Knight has recently been opening new Fountains. If too many Fountains are open at once, an apocalyptic event called The Roaring takes place. Titans emerge from the Fountains to devastate both the Light and Dark Worlds. Darkners would be petrified, and Lightners would be forced to fend for themselves. The Light World would become a place of eternal night.
As such, it is stated by The Prophecy that three "HEROES" are destined to seal the Fountains to restore balance. Sealing a Dark Fountain results in reverting a Dark World to its Light World form.
The Knight and Kris are currently the only known entities known to have opened Dark Fountains. However, any Lightner could potentially open their own Dark Fountain. This can be done by projecting their determination into a sharp object and piercing the ground. Berdly comes close to doing so near the end of Chapter 2, but is swayed against it by Ralsei's warnings.
Fountain of Darkness
The Fountain of Darkness, also referred to by Ralsei as the "Grand Fountain," towers above Castle Town. It is visible at or near Ralsei's Castle. In Ralsei's prophecy, he states that the Fountain of Darkness "gives this land form." It can also transform Castle Town if Kris recruits Darkners. Darkners who leave the Dark World that they originate from quickly grow weak, before turning into stone statues. The only exception to this effect is the Dark World shaped by the Fountain of Darkness. As Ralsei puts it, the Fountain of Darkness is "made of pure darkness," allowing all Darkners to persist.
The Eastern Fountain is the second Dark Fountain that Ralsei mentions in his prophecy, created by the Knight and threatening to upset the balance of Light and Dark. Reflecting the school's unused classroom, it stands at King's Card Castle, and is closed using the power of Kris's human SOUL at the end of Chapter 1.
The Library Fountain is the third Dark Fountain encountered in Deltarune, and the primary fountain of Chapter 2. The fountain is opened in the library's computer lab, and creates an electronic-themed Dark World known as the Cyber World. After travelling through the Cyber World, Kris uses their SOUL to seal the fountain.
The Library Fountain was opened by the Knight on the same day as Chapter 2.
In the final moments of Chapter 2, Kris, after forcibly removing their SOUL, uses a knife to open a Dark Fountain in the middle of the living room while Toriel and Susie are sleeping.
- Sealing Dark Fountains increases the party's LV.
- Immediately after being opened in the Light World, a Dark Fountain takes the form of an opaque black fog that seems to fill the room the fountain was opened in.
- The texture of the fountain is derived from the background of the Introduction sequence at the start of Chapter One.
- That Is When I Realized | This Power... This Power Of The Will | This Power Of Determination... | Is This Something That All Lightners Possess...? | If One Is Simply | Determined Enough | Could Not Anyone Make a Dark Fountain? - Queen, prior to her final battle
- (Kris, as you bring Dark World Denizens back here...) (The power of our Fountain...) (Will transform this town more and more.) - Ralsei, Chapter 2.
- The Knight | The Roaring Knight... | Today, It Deigned To Create This World | Reaching Its Long Hand To The Sky | It Coursed Its Will Into Its Blade | And Made | Thrusting The Fountain From The Earth - Queen before the GIGA Queen fight