Concept: super clever stuff, I love it! I really like how it combines some turned based strategy aspects with the random fun of the sack combining system. One of the most unique ideas this year for sure!
Gameplay: it's very fun, had a really good time. No bugs either, everything works really well.
The combining system is great, and I really like how smooth it is. I think it's a bit too random though, I felt like I didn't really have any control over the content of the sack, no matter how hard I tried to strategise it. Swords and wands kept piling at the bottom with no way to utilize them. I think some more controlled way of interacting with the sack like the ability to delete some items or shaking it in a specific direction alleviate this.
It's also a bit too easy, I've not lost a single skeleton during the whole game. Never even got to see what the unique kinds of skeletons do because of this, the difficulty should've kept ramping up infinitely I think, maybe even exponentially after some point. Though I know that balancing is a hard to afford luxury with these jams so it's fine.
The instructions should maybe be pushed in the player's face a bit more, I was kinda confused at the beginning before I saw the instructions on the top.
These are not a big deal though, just nitpicks from me, what you have is already very impressive.
Art: the spritework is really good and well polished. Also the opening cinematic is pure gold, please make more of these in the furture Jello.
Audio: pretty good, everything fits well with the gameplay.
Very impressive submission overall, nicely polished with unique and fun gameplay. Congrats!