i think we might have at least some reason to suspect what IMAGE_FRIEND is supposed to be.
from the /egg/ page of the spamton sweepstakes ARG, which is all about noelle encountering something awfully similar to another particularly infamous pokemon glitch:
and in the final section of chapter 3's mantle game, which takes place in the shelter:
combined with the glitch-like effects of the IMAGE_FRIEND instance in chapter 5 (not just the way it deals damage, but also its ACT prompt having no text and not showing a path back to the person using the ACT), i think the odds of them being glitch entities given form through a dark world are pretty high at this point - and that feels pretty notable given all the focus on game mechanics in chapter 5, and particularly the way the roaring knight, now seemingly connected to the day the shelter dark world was formed, is apparently able to ignore "fake stats" when normal gameplay mechanics can't.
...but, doesn't it stand out that the chapter 5 instance of IMAGE_FRIEND is completely harmless until you interact with it using the SOUL, at which point it turns red and inflicts damage in its weird glitchy way?
isn't it curious that the instance of IMAGE_FRIEND that can appear in the BATTAT minigame can both drain your points (a negative effect) and boost them by much more than any other cat (a positive one), but always drains your fuel to either 20% or 1% depending on whether you were already under that 20% mark or not?
isn't it peculiar that the cat heads in the shadow mantle holder fight act as minions for them, even if they're also able to drop hp candies that heal kris on every attempt at the fight beyond the first? (it's worth noting here that the mantle game intro shows the SOUL as acting through HERO_SWORD, but the shadow mantle holder fight - and only that one fight - shows both HERO_SWORD and kris taking damage...)
a recurring thing we've seen in deltarune is that darkners want to make lightners happy. even the flowers in asgore's shop are, ultimately, fundamentally inclined to be supportive of both asgore and the fun gang. if IMAGE_FRIEND is representative of glitch cats given form in the dark world, it makes sense that they're supportive of kris (a lightner) but hostile to the red SOUL (arguably a foreign entity, since it's tied to Us, The Player, even if it's tied to kris)... but both their role in the shadow mantle holder fight and their effect in the BATTAT game almost make it seem like their loyalty's a little... split?
i think all that talk about demon-summoning is relevant here, but to be clear: i don't think that IMAGE_FRIEND literally is the demon itself. but they're probably connected - and likely at least somewhat subservient - to the demon that kris communed with as a kid, and the shadow mantle holder encounter (which also has some really weird visual glitches going on, notably) is currently our clearest clue as to why, and what that means.
the thought that an entity that we've seen try to goad kris into violence, in the context of a game focused so heavily on getting stronger, being connected to reality-breaking glitch entities... is pretty worrying, to say the least.
...and a little familiar.
