This game is a lot of fun and has a very good concept. Has a bit of replay value too. There are a few things I would like to see though:
The heroes you get are fairly random. I would it like when you refresh your tavern, the hero that you used the cup refresh for, gets turned into a hero of the same star value?
On the note of heroes, maybe being able to buy a cup or at least a cup upgrade would be nice instead of leaving it completely to chance.
I would also like the ability to delete spells. When you click on a rune, you don't know which one you will get, and if that one spell fills your last of the 6 spell slots and you don't like it, you're stuck with it. I can understand the randomness being part of the difficulty and charm but the not being able to forget it is pretty frustrating.
The enemies seem to scale up pretty fast in the early levels, if you're screwed with the first couple of heroes you get, it seems impossible to go further without grinding.
Other than those issues, I'd like to see more strategy games from you :)