First off, the scotch tape on the cover was a nice touch, as was the Made by Humans bar code. I am not familiar with Mythic Bastionland, so I might not be the best person to give feedback on this.
The writing is super evocative, it reminds me of a prose poem. This is a very vivid location and the imagery is exciting.
I love the art as well, they look like awesome settings and I think seeing them will be "worth a thousand words" for the player in terms of grasping what you're going for.
After reading through everything, I'm still a bit confused as to how it all works together. Here is my understanding after reading: The Sea Knight seemed to me to be a player character option. I presumed that there was going to be a strong sea element but it seems like we're kind of in a land of streams and lakes and the Lady of the Lake is presumably in the lake with the Repentant Tears, judging from the image. The land is called The Tears and there is a cavern with The Sink inside it which is the main area of the adventure.
I'm not sure what to take from this, "gaping clouded maw delusion urging freedom the boon, at what cost" freedom from the boon? but I'm not seeing any other mention of a boon.
Again, I'm probably not the best person to weigh in on this because I don't know the system, but I think while the art and writing is very vivid, I would need a little more grounding in terms of how these elements are connected to one another in order to be able to run it.
Happy to answer questions if you have any for me!