Spoilers: Full spoilers from Chapter 2

Uh, there are a lot of these, since as I said, this chapter has some of the most meat on its bones. I'll try to list them in order, and we can split into further threads to discuss more if needed.

The Narrator is revealed to be Nemesis, one of the triad goddesses of justice. Argos prayed to each of the twelve, plus Hestia and Hades, before praying to the Eyrenies, 'those winged spirits of vengeance'; then finally this triad of goddesses: Dike, Themis, and Nemesis. She is called the Tilter of Scales and is a goddess focused more on vengeance and retribution, especially to those who suffer from hubris and arrogance before the gods. Thus her very brutal plan for Argos makes a lot of sense: in his own way, Argos and the whole Argoi role is its own form of hubris, and Argos must prove himself in trials to redeem himself and be worthy of her help. Vengeance is also a very brutal form of justice, and can easily spiral into cycles of its own, which definitely fits the themes of Minotaur Hotel.
Also, she often (only?) refers to Argos/Nikos as Orestes, in case you see that name thrown around.

Argos' Overseer, in case you didn't figure it out from Chapter 18, is Hermes. Which has really sad implications for Argos, since Hermes tries to get Argos killed in the favor of speeding up Hermes' plot(s) during the Chapter 18 climax. Protecc the Snek.

The godmade shrine that Nemesis directs Argos to is Poseidon's: It is a large body of water that was supposed to be saltwater, which would make it fall within Poseidon's powers of the Sea. However, the realm cannot generate salt in large quantities, so the shrine is incomplete and cannot grant the hidden Gift. This is where the artifact that Nemesis gave to Argos comes into play, though it isn't exactly clear yet what it is. Here's the text from the game:

He unwraps the artifact we gifted to him from the cloth that swaddles it, freeing that hunk of cursed rock from its hiding place. Dark as obsidian. Dark as the still waters stretching out within that underground cavern. Dark as the ichor which runs in the god's veins. It was no easy matter to steal it away form its origin deep within the bedrock of the realm. But by our contract with this usurper was that single shard granted.

With the conversation we had over in the spoiler thread about the importance of blood and Ichor in the game's mysteries (link here), I suspect it might be the actual drop of Poseidon's Ichor that was spilled to make the realm - thus it is one of a kind, as dark as Ichor (because it is Ichor), and it explains how it specifically allows the shrine to be completed.

While I didn't hide that much of it from the summary, I did gloss over a little bit of the ritual and Nemesis' explanation about it and Asterion's cairn shrine: 

Perhaps [Asterion] thought one of the old goddesses of his Minoan ancestors would grant the mercy refused to him by the Olympians. Uncountable are the years since libations were made at this little makeshift altar. First the ancient Masters refused the bull his private worship, and then Joseph the Merciful made it forbidden - along with all other rites to the "pagan" gods. Now, whatever power once lingered within it has long flickered out like an untended flame. But the prisoner's faith remains to this day, and a belief so ancient and wholehearted is no trifling matter. If you stir these cold ashes with your unshakeable belief, Orestes, something may manifest within this forgotten husk. It will be just like ancient times, before humanity grew too great; a single worshipper praying in a time of exceptional need so a god may be born.

And indeed, the ritual creates a new god, as when the speak (in caps), they are called Nameless Goddess and do not have a textbox decorator pattern like other spoken roles. (Oh and by the way, Nemesis never has one either, can make it a little hard to tell when she's talking, just musing, or narrating)

The power that Nemesis channels through the Gift into Argos to magic timeskip the pit digging is her own. I don't know if that means she doesn't have a godmade shrine here to channel through or otherwise write rules for the realm in, or if Poseidon's Gift is just that good a conduit, but I left out that it's her direct power she's flowing through Argos in some way.

What's left.... I think just that it's a little blink-and-you'll-miss-it that Argos/Nikos and his family are some flavor of Catholic, since they specifically say grace before they eat. That comes into more detail/hints both later in one of the endings, and in Chapter 18 if the MC figures out that Argos is the same Dominikos that claimed to be a preacher and befriended Asterion via text. I assume we'll learn a bit more on how that all works later in the story if we hangout with Nikos as a staff member.