To start I want to say that this was a very polished and unique game. The art, music, sound effects, and design all give this game a very complete feeling. Its an interesting way to twist the theme that provides a very unique style of gameplay.
First I want to talk about the art. There's a good variety of sprites throughout the game and they all maintain a high level of quality. Additionally you did a good job of building a sizable and believable town that makes for a simple but effective background for a mostly UI focused game (Not that it's bad, but were there any initial plans to either explore or have the fights more physically take place in the town? Seems like a lot of art for just the background).
Speaking of the UI, I really like the eldritch runes style that is maintained for all the different elements. From the title, to the intro, and the gameplay it really ties everything together. I also found the stat runes to be very clear and understandable, while also fitting into the aesthetic of everything else (I noticed that the "i" was using the Amplify rune, which is a fun detail).
Additionally, I really like the way you maintain the purple and orange aesthetic throughout the game. The colors fit the eldritch theme (At least I think they do), and
One minor detail I wasn't totally sold on was the font. It stood out to me among all the pixel art. And while I do feel that the non-pixel art fonts are often more readable, It does take a little bit away from how consistent everything else was in my opinion
As for the audio, I found the music to be very fitting. It loops well and was quite dramatic, without feeling to fast/intense for a puzzle game. The music on the title was a little abstract, but a good fit for the "spooky" eldritch theme.
Also the sound effects were really satisfying and impactful, which really helped make building out the board and watching the fights feel much better.
Next I want to talk about the gameplay. While the concept of building runes to create a monster is really cool, I have a few suggestions. To start I felt like I never had a clear goal when building my monster. Since I never knew what was coming all I could do was hope I got the pieces I thought were good combinations. If there was a little info on what stats my opponent would have each fight, I could have tried to play around what was coming.
Additionally, since I couldn't tell how much each rune actually buffed my monster by, I felt like I was guessing that certain combos would be good, rather than being able to actually "math out" a good strategy. It was also hard to tell what base stats my monster had leaving me with questions like do I have base crit/dodge, what's the base crit multiplier, how good is defense, and so on. I feel that showing me my own monsters stats as I build my board would have been helpful and made the game feel more strategic.
And lastly I felt that the actual rune building was a bit shallow. I feel as though I may be missing something, but since you always get 2 amplify runes the only consideration when building a board is which runes to pick and which should be amplified. Other than that, I didn't get a feel that positioning mattered at all, which made the gameplay feel a bit basic. I feel like introducing a 1 or 2 additional mechanics each round that leaned into the puzzle aspect could have helped give the player more to think about, and kept the game from getting repetitive. Things like "a diagonal line of runes gives this effect", "you can't place 2 of the same rune next to each other", or "this tile is now cursed, adjacent runes are 0.5 times as effective".
Overall, this was a very impressive game with great direction and style. I apologize if this review was a bit much, but I'm doing this to all the games from this jam as I think critiques help us grow.