Absolutely adore the concept, but requiring an account is a bit of a deterrent, maybe think about ways to have non-account connected/offline versions (perhaps localised with only bots?), and currently the difficulty for a new player raiding their first dungeon is too high. (spending gold on traps and monsters to then realise you can only afford three free heroes means your account is soft-locked, since I was defeated in the 5+ dungeons I attacked with them after that).
Perhaps a button/option to reset your account data would prevent the initial soft-lock?
Other than that, it was enjoyable, and I really do hope you keep developing it further.