My interpretation of the plot.

I know this is probably wrong, but this specific interpretation I came up with scratches my brain in a way that makes me feel like it is a half-decent theory.

First off, I think that everything that happens in the game is real, and that the "government" (which I think are world powers), are in fact keeping everything under wraps, especially our favorite giant firefly.

In the song that plays after the ending, the entire set of lyrics talk from the perspective of one person to another, describing how they found where they were (the catacombs), and that they were taken apart or used to keep the world functioning.

I think this whole song is from the perspective of the main character talking to the queen of Venus, and that Venus was trapped underground and used by the people in charge to fuel humanity and keep them in charge, which explains why all the Thraits and other species are stuck underground.

I believe that the main character actually becomes Venus at the end of the game, and starts as a normal person. The main way I think this is possible is that Venus possibly possessed/made the main character a new host(?), and that's why we only see evidence of the queen (the molt), and Pompy's ascendence at the very end. It is also apparent that the queen has been physically in the catacombs way before Pompy's visit, which would track with Pompy not being born as the queen of Venus.

I think it is very well possible she was being subconsiously influenced by Venus though, which may be a cause of her insanity. The house section is important here, which I think is some odd time fracture anomaly that would fit right in with the rest of the catacombs. The tv talks about a giant insect breaching the surface and being spotted in a city, and I think this is a childhood memory of something that the elite wiped from the minds of the public, but also something that the Pompy never forgot one way or another. This event may have very well been around the time that she started to become less mentally stable due to the influence of Venus.

This negative view of Venus during her childhood may be why the ending song says, "They told me to cut you to pieces". The world leaders obviously wanted to keep using Venus, and painted a negative picture during the news report, showing her as a destructive monster.

The cutscene dialogue during the epilogue also makes me think that Pompy was being manipulated, because the speaker knew that she was headed towards Venus, so there had to be some level of connection between them.

As for Mercury, I think that after Pompy became the new Venus, she destroyed most of her own earth because of how corrupted she saw it (she mentioned it in the main game's ending cutscene) and is moving on to killing Mercury next, as he is her polar opposite by nature. This is why the king of all dogs and the rest of the family team up with him. He is also technically not "Mercury" right now, but will eventually become the next Mercury and ascend just like Pompy did to stop his own planet from being destroyed.

So I think that Psychopomp 2 will be similar to the first game in that it will be about a person delving into dangerous places and eventually ascending to godlike status after getting far enough.

I am fully open to this theory being 100% wrong, but I though I would put it out there seeing as there aren't as many threads talking about the game's meaning as I thought there was. Feel free to correct me on things or ask questions!