Bad Boys, Bad Boys

Question: Making this question short (pun intended) - how would you guys handle the legend of Procrustes, Poseidon's other (in)famous son?

Sometimes, Scions go bad. It's a thing that happens. They might go bad because they've been mistreated by their parents or pantheon, because they've suffered some misfortune that permanently scars them, because they've been corrupted by a minion of the Titans or even just because they were flawed or unstable to start with. That doesn't mean they can't still do awesome and legendary things, but it usually means those legendary deeds are not the most positive the world has ever seen.

Procrustes, the infamous king who forced travelers to fit into his guest-bed by either stretching them with rack-like tools or cutting off limbs that were too long, is one of those Scions-gone-bad. No myth explains why he was hell-bent on murdering any traveler unfortunate enough to come his way (except maybe a side implication that he did it in order to rob them), but the crime of breaching the sacred rules of hospitality was one of the most serious and swiftly punished in ancient Greece, and he was inevitably put down for his actions.

It's probably not a coincidence that Theseus, another Scion of Poseidon, was the one to kill him. It's likely that Poseidon himself refused to tolerate his wayward son's actions, and sent his brother to provide swift and brutal punishment.

Sky Versus Sea: Fight!

Question: Do you think the episode of Set, Nepthys and the sea could be played as a conflict between Set and Poseidon?

I think that if you have a fun plot you want to spin off of that, sure, go for it. Egyptian mythology really doesn't have a sea-god thanks to their focus being narrowed down mostly to the Nile and surrounding environs, so there's no easy Egyptian figure to attach to the myth and the personified sea is merely itself. There is also no hint of any Greek influence in that particular myth, but Poseidon is the Greek god of the Mediterranean, and if you wanted to play it as an ancient political grudge-match kind of thing, you probably could.

Interestingly, I've seen scholarly suggestion that that particular myth might be heavily influenced by Canaanite mythology; in an alternate version, Set is instead married to Astarte (who was given to him as a sort of consolation prize after he lost the throne to Horus) and it's her he's saving from the ocean, which therefore probably refers to Yam, the Canaanite sea-god who's always startin' shit. This is probably a result of the fact that Egyptian and Canaanite territories overlapped and that Set and Baal, being both bad-tempered storm gods, might have been slightly conflated or worshiped together by some Egyptians in that area. If you wanted to, you could probably consider it a purely Canaanite myth and decide that it's referring to Baal, not Set, when it talks about going out to fight the sea.

Either way, though, the sea, whoever he is, is going to take a serious pounding to the face if he keeps these shenanigans up.