When Luz and Hunter first arrive in Belos' mind, they find a gallery of memories showing Belos to be a benevolent leader. However, they all look very stylized, similar to Eda's wanted poster or the murals painted in his castle. If you remember "Understanding Willow", Willow's memory gallery looked like a series of photographs. This can be seen as a tell differentiating a Self-Serving Memory from a real one; he literally painted a rosier version of the past.
The Golden Guard's mask is to keep anyone from realizing that Belos is cloning the same individual over and over again. (Though, Belos' comments imply the Grimwalkers don't look exactly alike.)
The trap Inner Belos springs for the Palisman Monster utilizes a series of potions that looks an awful lot like the elixirs Eda uses to keep her curse in check. This draws an uncanny parallel between the Palisman Monster and the Owl Beast, Eda and Belos needing a special form of mental magic (Eda ingesting sleeping nettles, Belos getting Luz and Hunter's help) in order to gain control of their more beastly halves. But whereas Eda learned to live alongside the Owl Beast, having had the curse thrust upon the both of them unwillingly, Belos's condition was self-inflicted and he seeks to purge himself of the problem entirely, destroying countless innocent palismen in the process.
Likewise, the background paintings in Belos' mindscape reveal that Philip had a similar relationship with his brother as Lilith had with Eda: They were close as children, shared a childhood dream (joining the Emperor's Coven for Lilith and Eda; becoming witch hunters for Philip and his brother), then later grew to resent and betrayed their sibling. However, while Lilith didn't mean to permanently curse Eda, rightly blamed herself, and dedicated her life to fixing her mistake, we see from the hidden dagger in Belos' mindscape portrait that he did mean to kill his brother, blames said brother for his own murder ("it hurts every time he chooses to betray me"), and is not trying to fix his mistake by bringing his brother back via a Grimwalker, but openly tries to make a "better version" of his brother (read: more blindly obedient), and kills and discards any Grimwalkers who "betray" him too.
Hooty's new defenses are a quite an upgrade to what we've seen before—usually, it's just Hooty who takes care of everything, and magical defenses were usually done by Eda, back when she could still cast magic. If you remember back in "Eclipse Lake", Amity wanted to beef up the house's defenses, and these new additions (metal shutters, barbed posts) were added/created at Amity's suggestion.
Of course Kid Belos wouldn't be the manifestation of his guilt as Luz speculated. Belos is proud of being human and if Luz and Hunter had seen the real portraits in the background depicting Philip's childhood, they would realize that being a human child playing games is where Belos felt most happy. If Belos did have guilt or regret, it would have manifested in the form of the monster underneath, representing the undeniable truth that Belos is no longer human anymore.
Just how many times was Hunter killed and replaced over and over again by Belos?! If the old, discarded masks seen around Belos' true mindscape is an indication, it's at least 16...
Assuming Philip has been in the Demon Realm somewhere between four hundred and three hundred and fifty years, and that he’s only made sixteen Golden Guards with none being created at the same time, then that means the Grimwalkers on average live for about twenty years before Belos kills them.
A key ingredient in Grimwalkers is a bone from the one being copied, presumably where the DNA blueprint comes from. The adult human body has two-hundred and six bones, and while the dialogue implied that quite a few Grimwalkers had come before Hunter, there was also little indication of Belos running low on bones.
In "King's Tide", King stumbles upon a pit within the head of the Boiling Isles, where Belos had been dumping the remains of all the past Grimwalkers. What appears to be well over a hundred masks and bones can be seen lying within the pit.
How many innocent witches has Belos killed, either as part of a False Flag Operation against wild witches or in testing out his sigils?
The Palisman Monster sounds like Fryda Wolff, who also voiced Kid Belos and the Collector. Luz mistakenly believes that the Kid Belos she encountered is the manifestation of Belos' guilt, not realizing it's Inner Belos fooling her. And Palismen don't usually speak like humans, especially the ones consumed by Belos. If it's possible for two inner manifestations to be inside the mind, then there's a possibility that the Palisman Monster is Belos' real manifestation of guilt, forcibly fused with the palismen he consumed and desperately trying to fix his mistakes. And Inner Belos killed him.
