Seam could be the next secret boss
BIG CLARIFICATION: THIS IS MORE OF A SPECULATION THAN A THEORY, SO TAKE THIS LIGHTLY
The basis of this idea is very similar to the one about FRIEND, being that the pointed tail prophecy is almost grouped with the one about Asgore, meaning they'll likely both be in chapter 5.
First of all, this will probably be the first time Seam doesn't warn us about the upcoming secret boss. Of course, someone could argue that we had to wait for Chapter 4 for him to talk to us about Gerson, however if chapter 5 is festival day then the school could be locked, meaning that we likely won't get to talk to Seam.
Also, his and the shop's colors seem to be very close to pink and gold, just darker due to shadowing (here's what he looks like with slightly shifted tone and higher vibrancy)
His role in the story, how it always seems like he knows the future (due to knowing the upcoming bosses), also probably has full knowledge of the prophecy which could be the reason "nothing matters" in his eyes, all make him one of the characters we know least about.
One more thing that comes to mind is the fact we have never seen his tail (or his full sprite in general, and even in the light world we can't see his tail). And since the biggest argument that DEVICE_FRIEND's tail is the one that will take crawl is based on it's cat-like appearance, I don't see why someone can't make the same argument for Seam.
After all, it would be very poetic that the last crystal would be held by the one that's responsible for them. Obviously he owns more than he sells, since he held the Mantle (which was first mentioned in chapter 2) and part of the Jevil's broken key (which he did not give you from the start either).
Maybe he would need you to prove you're strong enough to hold the PureCrystal, or pure enough to deserve it.
Furthermore, although this is very speculative, we could get an Asriel appearance in this upcoming chapter, since his connection with Seam is implied by checking his computer in the start of chapter 4. So, maybe he will search for Seam and get him to play a more active role.
One more thing I want to talk about here is this hidden NPC dialogue
Of course, this seems to describe Gaster (the Mystery Man, which by this point is almost confirmed to be his appearance) VERY, VERY well. However, I would like to point out that the cut seems to be on the side of the eye that is still there (the button), as well as the use of the word "weaves" which fits well with the idea of a woven cat.
Something I would like to point out that goes against all this is the way Seam seems surprised when we are able to get each Shadow Crystal. Lots of questions can be raised around that matter, like
- "Are the shadow crystals part of the prophecy?"
We can't know yet. There has not been any mention of them - maybe except one.
If we go with the popular assumption that the second hero of the prophecy is Noelle Holiday *which is incredibly likely, since Susie has a different prophecy, one with the rude buster icon, that implies the two girls are seperate*, we can also see her holding a sword. Of course, we do know that Noelle can hold some of our items, but it could be the TwistedSword, which needs the PureCrystal to be created, the one that is made out of 5 ShadowCrystals.
- Why does Seam gain hope when he finds out you defeated the bosses and got the crystals?
This is also very vague. On one hand, Seam's reactions make a valid point against him knowing the prophecy. On the other hand, he makes it sound very doable and maybe irrelevant to the ending. When he talks about fighting the Knight in the end of chapter 2, he says that while the fight may be impossible to win, with the help of the ShadowMantle. So I can assume the reason he was surprised you won in chapter 4 was more so because you got the mantle, which maybe confirms the prophecy (meaning that even if someone tries to change it - King for example, where he presumably used the mantle from Seam, at the end things end up how they were supposed to).
- Are the secret bosses, in general, in the prophecy?
Yes. Two panels prove this:
Gerson's Hammer of Justice prophecy
The Knight dueling with the heroes (secret boss also)
That's all I have, I'd love to hear your guys' thoughts on this.
Big thanks to my gf u/foustanella33 for the help and suggestions!
Posted Sep 3, 2025, 6:16 PM UTC