Art and sound are very nice and the mechanics are interesting.
I feel like the battles are a bit too long and maybe could use some faster/stronger upgrades (maybe counterbalanced by increases to enemy damage). The choices of attacking or upgrading and swapping out monsters are interesting, but often left me feeling like I wasn't progressing much each turn.
Overall the game is very interesting and well made; maybe could use some balancing and some additional cards? But that's very much true for most games made on a time limit :)