Congrats on your game! Sadly I was not able to find the dungeon king, it really felt like I cleaned the entire dungeon,
As pointed out below the mana restoration is a bit slow. Its also odd that the line of sight of the enemies is so short, you can just stand and pick them off from a distance.
When I started the game I also briefly saw the dungeon king but then died (?), not sure if that was a glitch or if I just immediately found him. Nonetheless well done, making a game in 4 days is no small feat!