The default ending of Final Judgment is inspired by a part of the Bad Time Trio comic where the Trio kills you and forms a column of bones around CharaFriskMetta, but in the fangame Chara opens a "dark fountain", which is not a dark fountain, it's more like a very strong attack that looks like Chara is opening a fountain.

The "structure" of the solo fight against Chara (Vehement), is based on One Left from the AU Call Of Void.

Chara not letting herself die, and becoming determined to kill you.

Chara using the save to bring Sans and Papyrus "back to life"

The Player losing in the end.

Random curiosity, One Left was my favorite song before Vehement.

In Final Judgment, at the very beginning you can see the Great Time Trio transforming into the Bad Time Trio, this is because in the game's history the GTT and BTT timelines are connected, the player used the glitch that brought the BTT to bring the GTT instead.

(The entire story of the game is based on the Player looking for a challenge, all the Rerun fights are the Player trying to make other endings and make this trio reach the limit.)

In the Capture The Human fight, the Chara in the background was supposed to appear more like a ghost, but because my PC and skills were much worse at the time I started doing this fight, it ended up being a lot of work to do this, so I just made the Chara darker in the background, instead of making her look like a ghost.

The Bad Time Trio fight only exists in the game because I had already made their sprites for Final Judgement, so I was like: If I already drew them, why not add them to the game?

And this fight was the first Extra in the Game.

A lot of the story isn't told in the game because making dialogues and cutscenes is difficult, and I also thought that people wouldn't be as interested in the game and its story.
(I was wrong.)