Wow, there is so much potential and excellence in this painting. I shall evaluate each frame by itself to give a more effective review. :)
1st frame: I can tell that the space atmosphere is full of detail that took quite some patience to complete. You do not get such a well balanced combination of colors and stars without patience. After looking through all of the frames beforehand, this one is my favorite.
2nd frame: There is some lovely detailing here, but there are also flaws. The man that is shaded mostly grey and a little to the right of the goddess in the middle has a very bulky and misshapen left arm. The legs of the man right beside him are too short for his stature and his feet are awkward looking. I also see this issue with the left foot of the man I mentioned before and a couple others in this painting. I'm not sure if the feet were intended to be drawn that way, but either way they do not look well done and therefore, not impressive.
3rd frame: The detail is great, the layout of the land is substantial, and if the smoke from the volcano is supposed to be creating a dark cloud in which the lightning is striking down from, it is a magnificent and creative idea. It also has kind of a cartoonish vibe to it, which I like. One thing I did notice though is that the white clouds near the cracked part of the volcano with molten lava inside should probably also be dark. The same kind of issue falls upon the cloud that is below the big dark cloud of smoke that is emerging from the volcano. That should not be white, since it's so close to that cloud of smoke.
4th frame: I know you uploaded this piece of artwork alone and it is a very well done piece, but I feel as if the mountains are not detailed enough. I feel that you would usually add some more detail to them in a painting of yours. It kind of makes the quality of the mountains stand apart from the detail of the ship and water, which are more well done.
5th frame: I can see that this piece was done to show the murkiness of an underwater marine environment (or maybe that's just me). At first, I thought this should've been more detailed, but it actually captures a more realistic outlook once I thought a little deeper.
6th frame: This last frame is a very interesting piece. How I comprehend this painting is that it's deeply below the ocean as the entrance to Hell or the Earth's center. The demon depicted is nicely detailed and holds well to his fiery environment. The lava behind him is a nice touch, since the light illuminating from it reflects off of him, creating a more sinister vibe.
There is definitely some work that needs to be done on some of the pieces, but they all hold great potential. One thing that I did not mention is that I love how all the frames blend together, that was a brilliant idea. I saw in your Author's Comments that this was a collab, so I hope that they can receive this constructive criticism from you, perhaps. I want all artists who worked on this collab to see where they can improve. :)
You did a good job, nonetheless, and same goes for the artists you collabed with.