You've mentioned that the Horrorterrors are a fundament of the game along with Skaia, but there appears to be a clear scene in the Credits where a ghost player is becoming a Horrorterror. To me this makes sense and the Horrorterrors are created when the Paradox Space of the Furthest Ring is destroyed; they're part of the main loop and partly responsible for their own creation. They're the fragmented and recombined memories of all the dead players of every possible timeline. Thoughts?

Horrorterrors are the ‘Eldritch Forces outside of the Universe, bent on preventing the Birth of a new Universe’ to Skaia’s ‘Unfathomable Force of Light that wishes to aid in the Birth of a new Universe’, they’re not as much of a Fundament of the ‘Game’ as they are an important part of Paradox Space. However, ‘a clear scene in the Credits where a ghost player is becoming a Horrorterror’ is simply not true. It may subjectively look like that to you, but I couldn’t find anything that even remotely resembled that, let alone ‘clearly’, with the most I could imagine being what seemed like either a God Tier John ghost or a God Tier Equius Ghost, maybe Mituna, with the long hood being dragged back and towards the Black Hole. There’s a big headcanon going around about God Tiers in Doomed Sessions just getting weirder and more Eldritch and becoming new God Tiers, but for this to happen to the ghosts while everything is Collapsing seems a tad weird and kind of… Looking more into it? Not that it couldn’t happen, just that I don’t see it from the snaps we get on the Credits at all.

There’s an interesting distinction to be made here about Paradox Space and the Furthest Ring, too- And that is, unless the nature of Paradox Space truly is circular, and the Black Hole leaves a blank slate behind from which Paradox Space can be born once again, and cycle back to the very beginning of Time (Which could happen), this is the Ending. As in, the end of the road for the Furthest Ring and Paradox Space. There’s only going forward now, not backwards, because the Cracks in Paradox Space stabilize the flow of Space and Time through the Furthest Ring. They make it less Non-Euclidean. So unless, as I said, Paradox Space is cyclical, and the stuff that’s there now could become the stuff that was there at the very Beginning, ironically enough, everything Collapsing means that things are the most stable they’ve ever been, and there’s not quite a way to ‘go back’ to a point before what’s happening right now.

Golly, the Ending sure is Weird! I do love talking about the Ending though, and the implications of everything. Say what you want but personally, Act 7 and the Credits are my favorite part of the Puzzle Homestuck is, and I adore trying to unravel everything about it.