- "I just want to come back..."
"destroying everything in your path is not the right way, G."
"I'll use any means necessary." - ―W. D. Gaster and Sans[src]
The Battle of Waterfall was a battle between Sans and W. D. Gaster in Waterfall, Monster Kingdom. Willing to become whole by obtaining Frisk's SOUL of Determination, Gaster attempted to kill Sans, who had absorbed Frisk's SOUL. Sans' actions, however, resulted in the attack on himself being neutralized and the timeline being reset.
Background[]
The background is darker blue and a bit darker blue in the bottom, there is a door which closes if you go in.
Battle[]
W.D. Gaster explains that he can be whole using frisks determination soul, he corrupts the reset file and says that he cannot allow it, he tries to hit frisk with a gaster blaster but sans blocks it using a bone, sans tries to teleport but forgets he cant so he blasts the door open allowing some space and also allowing gaster to turn to his outside form. Sans decides to combine with the soul but gaster stabs him with a tentacle and gaster takes the soul, but it refused, allowing sans to get the soul and becoming stronger than he is, gaster summons his 7 hands and makes a blast trying to hit sans, it follows him around and sans flies to the air, only to discover they surrounded him, he blocks the blast with bones, he sends the bones and gaster blocks them with the justice hand, sans dodges the attacks and uses a bone to break the hand, W.D. Gaster gets suprised by this and almost gets blasted but he uses the kindness hand to make a shield, he tries to crush sans using the same shield but sans easily breaks it causing the kindness hand to break aswell. The patience and integrity hands attempt to kill him by distracting him with the patience and using the saw to kill him, sans gets distracted but uses the saw to break the rope and uses them agaisnt the hands breaking them, W.D. Gaster attempts to bomb sans using the bravery hand but he dodges it 3 times, on the third one he grabs a tiny one and bombs the hand. W.D. Gaster realizes that if the hands break, he gets injured aswell. W.D. Gaster attempts to blast sans with the perseverance hand but sans creates a gaster blaster, being tied with the hand, sans sends 3 bones to attack the hand but the hand sends 3 bones aswell causing the bones to break and make a tie, sans teleports to the air and surrounds the hand with 8 gaster blasters, the hand tries to defend itself but it breaks causing W.D. Gaster to be injured. He tries to do a last resort using the determination hand sending a blast but sans easily dodges it, W.D. Gaster explains that sans does not understand to be abandoned, to be helpless, to be forgotten and tries to blast him with 2 determination blasters but sans dodges it, he makes a determination blaster, only that it is bigger and stronger but sans blocks it with a bone, W.D. Gaster attempts to blast him from behind summoning 5 determination blasters but sans uses a gaster blaster to tank it. W.D. Gaster reaching his limit causes the determination soul to break and leave him with no hands. Sans explains that destroying everything in your path is not the right way, W.D. Gaster says that he would use anything necessary to win and attempts to backstab sans with a tentacle but sans summons 2 bones to stop the attack. Sans resets causing the timeline to restart.
Aftermath[]
Sans explains that there is consequences to resetting alot without care, he explains some side effects will happen that frisk won't like, sans says that if the more they screw with the timelines, the more are the chances of bad things like something that is not supposed to be here appears he tells to frisk keep up an eye for things that seem odd.