>>527564381
The boss talks about the mantle as if it's something it's holding, not that it actually IS the Shadow Mantle

>>527564410
Kris's red horn headband that their parents gave them as a kid after Kris asked when their horns would start growing, after "wearing it for months" it disappeared
The Mantle boss
>Is initially hidden behind a door with a red devil horn frame
>Uses fire magic, like the Dreemurrs in Undertale
>Uses bombs, like the bath bombs Kris blows up the toilet with
>Knows Kris well enough to guess what's going on in their head, including that a part of them is enjoying all the shit (You)'re up to
>Specifically wants to see Kris engage in dangerous and violent play and their eyes "flickering red," and talks like this is how Kris used to be
>Fought inside the Shelter which is almost definitely where Kris was traumatized, and probably where Dess was disappeared
If the boss is an item that represents things Kris has tried to leave behind, like their dream of being a monster and their implied violent tendencies, and is an item that Kris would have been wearing while in the Shelter, then the horns would be the best candidate