for the delatrune theory, its that the theory about a 3rd route is true, but not in the way the guy (spookydood5500)making the video talking about a 3rd route said it would be. he theorized that this 3rd route would come after you beat jevil, play the chapter 2 weird route, and once you get the thorn ring you abort the route. collect the rest of the shadow crystals, and then in chapter 6 give the 5 crystals to seam and he will turn them into a pure crystal, which can be combined with the thorn ring and a sword (i cant remember its name) to make a new sword (cant remember the name) that you kill ralsei and susie with and kill your entire town with everything in sight. he uses a lot of his evidence from the mantle minigame in chapter 3, stating that the minigame is not meant as a introduction to the weird route, but is actually meant to fool you when in reality its for a new secret route called the sword route where its basically circling back to old theories that there would be a geno route where you just kill everyone. where i dont believe this is that that he contradicts himself saying that the snow route isnt breaking the game like we think it is. most think about the snow route in a way that its forbidden and not meant to be played, and spookydood says thats wrong because if you and noelle drown together then the game asks what we think is gaster to input chapter 7, meaning it was planned for. and that this sword route is whats actually unplanned for, but if this sword route is not planned for why is there just directions on how to do it in the game, in a game if we believe his theory. that and i just dont think toby is gonna add a geno route to the game just because he already did that, and seeing as the prophecy requires a human a monster and prince from the dark. now you can interpret that as them sacrificing themselves in chapter 6, willingly or unwillingly, to make kris have enough EXP/LOVE to stop the roaring, but i dont think that would count for the prophecy to work, and the entire game is about how your choices dont matter, no matter what you do the game will end the same, and prophecy come true. i think a more plausible theory is that after chapter 5 you abort the weird route which is what causes this new route to start. its a route in between the weird and normal route. in this world instead of you and noelle dying/changing forever because of the incident, and instead of your growing friendship with susie and noelle and you not hating the soul as much, in this route its a mix of both. you stop grming noelle, but shes changed, shes gone of the deep end and is mentally scared and traumatized from everything, kris despises you for what you put him through, and your relationship with susie is tearing at the seams with everything going on. noelle and susie dont end up working out from problems between the 2. thats what i think for a 3rd route is. now this theory doesnt have ingame files or things, but theres nothing really going against it, nothing stopping it from being true. now this route would be very different because of these changes in the world, not just that these relationships die. but i cant predict what would happen if this is true as theres simply 2 much guessing that would happen if i did try to give an idea of what would happen different to the actual gameplay not just flavor text and peoples personality. this theory may not have tons of evidence from the files or anything, but from what weve seen in the actual game i think this could actually happen, and theres nothing going against this theory. anyways this is probably gonna be a tadc episode 7 situation.
heres the video with the theory by spookydood: https://www.youtube.com/watch?v=7PZrJST8qko i think the theory is just people wanting a new sans boss fight thats official/j