I think this game has a really neat concept for the battle system, and I like how it ties into a sort of rhythm game. But I also genuinely think it needed a bit more time in the oven.
I know from reading the other comments that the big issues are clear to you now, but to summarize my thoughts briefly:
There's not enough enough spells and far too many runes currently, and the system is not explained all that well in-game. I appreciate that you uploaded a video example on the game page to explain it, and even actually gave the first spell as an example in the game menu. But even with that it took some time to fully understand what was going on.
Beyond that, the performance isn't great, or at least wasn't for me. This seems to be a common theme with Unreal jam games especially, and I can see from the video you posted it's not an issue for yourself. But I bring it up because I think it caused issues with click detection on the runes. I would click the rune while it was highlighted and the game wouldn't detect it as being a valid click.
As for suggestions for improvements, I think the position of the healthbars and their colours should be changed. The players focus during combat is largely on the runes along the bottom-center of the screen, but to check the enemy's health the player has to look to the top-left. Since the rhythm game doesn't have breaks between cycling rounds, there's very little time to look away, especially in the last couple battles.
And with the healthbars transitioning from red to black, on a black background, it can be harder to tell what percentage health an enemy has left as the fight goes. Without focusing on the healthbar at least. And the players healthbar had the same issue, especially because the player healthbar goes from right-to-left, despite being in the top-left corner.
I would recommend moving the health bars to be just above the runes, and changing the colours to be either solid, or simply make them brighter, or make the transition green-yellow-red instead of red-dark red. Just my 2 cents.
Back to the positives, the visuals are nice, overall the game feels quite cozy, and I liked the dungeon inside the chicken coop with all the stereotypical dungeon traps. There's some solid work here, but the combat system needs some fixing.
Good work!