I really liked the game!
I think there is a bit of a control issue, as many have pointed out already. Maybe the most basic auto attacks, that we start out with could be on LMB and RMB. It would also help with that whole mana management when you need to turn them off to get enough mana for some other spells. Also game felt a bit too easy at times. Player can spawn the minions in between heroes arriving and recover mana + the heal after every fight makes it just so you need to not die and can lose as much HP as you want. Though maybe that was the vibe you were going for, in which case great job on that! Because the player can feel as a very powerful boss. Oh and one technical issue I encountered was that the last enemy didn't heal himself even though he had multiple potions. Other than those couple things though, great game! The voiceover is amazing and fitting to the entire theme of the game. Also even though I saw a bunch of the "you are the boss" games, personally this one was probably the most fun and engaging from the very start.
Overall congrats on making an entry, good job!