Also, one of the rare things that's sure about them is that they all met Toriel in the Ruins.Despite their rather unclear morality, all of them aid you during the battle against Flowey and eventually rebel against his control to save you.Empathic Weapon: Even after death, they can still feel emotion and respond to your fight against Flowey.In fact, all of the SOUL traits are implied to be their own source of DETERMINATION. Though obviously they weren't as determined as Flowey or Frisk. Determinator: The purple SOUL's special trait was perseverance.The blue SOUL was wearing a tutu and ballet shoes, with the shoes being the weapons. In addition, the colors are indicative of the humans' greatest virtue before they died: Cyan - Patience, Orange - Bravery, Blue - Integrity, Purple - Perseverance, Green - Kindness, and Yellow - Justice. Notably, the colors correspond to the various colors that bosses can turn your SOUL, as well as the three different attack colors. Colour-Coded for Your Convenience: Separately from your red SOUL and white monster SOULs they come in orange, yellow, green, cyan, purple, and blue.Chef of Iron: Implied of the green SOUL, who used a frying pan as a weapon and wore an apron.And when he uses his save state powers to undo his defeat, they unite to utterly destroy him in one shot, saving Frisk from a truly unwinnable situation. Big Damn Heroes: After calling out to them enough, they resonate with Frisk and begin turning the fight against Flowey.
In the Neutral and Pacifist endings, they're all finally set free.
Gaster and his followers are characters hidden in the game's code with an unclear identity. You, as in, being a separate entity from the actual player character, spoils the fourth wall breaking aspects of the Pacifist and Genocide endings.
Turns out the child from the opening movie isn't the character you're playing as, and in a Genocide run, that first Fallen Child destroys the world. Chara/The Fallen Child spoils the Genocide ending, and to a lesser extent the Pacifist and Neutral endings as well.The Amalgamates spoil much of the pacifist ending since they are only found in the secret area known as the True Lab, where Flowey was created.
Problem is, that boss is built around trying to make you feel hopeless, so if you know how to beat him going in, the effect is ruined.