hots fireguy is the knight. the reason? they're the only one who remembers their own "name" which means that nobody else knows about their existence, much like it is with "mr. gaster". this means they were ERASEd from reality, likely by chara, as they're the only one to give us the ERASE option. and you know who else was ERASEd from reality? gaster, likely to be the knight's "friend" (much like image.friend.jpg, another "friend" of theirs)
another fact that supports this theory is the fact that their "name" changes in between undertale and deltarune. why, you ask? to throw you off. "hots fireguy" aka "heats flamesnan" wants you to believe they did not shatter between time and space like "mr. gaster" and therefore changed their name between the two universes they were shattered to. this has a connection to kris, who also changed their "name" when "transitioning" from one timeline to another. in "undertale", they do not appear, but we know they are there since "noelle", their "friend", is also there. we know they changed their name, since no one mentions "kris" in undertale, even characters who canonically know them (toriel, mettaton, "mr. gaster"). this has a connection to the knight, as kris is the knight's "friend" (much like image.friend.jpg, another "friend" of theirs)
now, if you look at hots fireguy (aka "heats flamesguy") they look unassuming. that is also to throw you off. if you "grayscale" an image of "hots fireguy", a hidden message appears: they have turned "gray", much like the gaster's followers turned "gray" when they were ERASEd from reality by chara's "machine" (or "device", as the "device theory" suggests), as entry number 17 was not written by gaster but by chara. by turning an image of them "gray" we have turned them into a shadow of their former self, much like the knight turned into a shadow of their former self when they ventured to the "bunker". this has connections to the knight, since we can also "grayscale" an image of image.friend.jpg, another "friend" of theirs.
perhaps the biggest peace of "evidence" is "mr. gaster" himself. in 2018, gaster appears in a sequence known as "image.depths.jpg", an image created in the year "2024", and the image used by image.friend.jpg to create "the prophecy" in deltarune. this means gaster can time travel. if you "overlay" an image of image.depths.2018 with "hots fireguy", they will look exactly like "image.depths.2024", which is likely not a coincidence. this proves they have a connection with "dark fountains" as the dark fountains are a metaphor for "water", and so is image.depths. (additionally, image.depths.png is an "image", much like "image.friend.jpg", a "friend" to multiple people we have discussed thus far.)
so far the pieces of evidence are: heats fireguy's connections to "the gaster", "chara", "kris", "grayscale", "image.friend.jpg", "image.depths.water", "ERASE", "entry number 17", "spamton", "dark fountains", "time travel", "the prophecy" and "noelle". but what about the knight? well, if you try "grayscaling" the knight, nothing happens, as they are already "grayscale". this proves the knight must've been "grayscaled" in the past, likely by chara or "mr. gaster". as hots fireguy can be "grayscaled", this confirms them as the most likely knight candidate. but if you put an image of image.depths.com over the knight, they will look like image.depths.gaster, much like hots firesguy (and much like another character, but i seem to have forgotten who it was). this proves a "connection" with the knight, much as gaster forms a "connection" with us in "deltarune". therefore, the theory is all but confirmed.
This is genuinely beautiful. You’ve done it. You’ve made the best possible Deltarune theory. I have no reason to update this blog anymore, because you’ve already created perfection.
(Day 76! Thanks for the submission ^ ^)