So I've beaten it on normal and I've beaten it on hard, currently on expert and making my way to Hell. After you beat the final boss you basically just save your current progress so when you load you start from the beginning again (the first option on the main menu is load game, by the way). The bottom option of the main menu is difficulty select from normal to hell. Some things that I've found:
Your plain ass C move, the boulder magic you get after beating the slime the first time, is literally just the best magic you have. The beam and wind ones are nice because of their range but the boulder only takes 15 mp and does a ton of damage when you land it, compared to the 30 and 50 the wind and beam cost respectively.
The treasure chest costs money to close it but every time you open it you get a random item. This can be from the basic bitch 100 gold red potion to actual upgrades to your shit, including your mace for more damage. The more you close and open it, the more it costs and in turn i think the better the items you can get. Eg you cant just run into the next level, lose, quit back to the hub area, and open the chest for free and expect an upgrade.
MP potions are pretty much worthless, they cost a metric ton and give you close to nothing back. The second one alone costs 5k to buy and only gives you 40 back, the 500s only give you i think 5 or so. You end up getting an item at some point that gives you MP back dependent on how big your combo is when it ends.
The item shop, that I have seen so far, goes as the following. Level 1 Hp potion for 100, Level 1 Mp potion for 500, Level 2 Hp potion for 800, Level 2 Mp potion for 5000, Combination Potion for 7000 (heals both Mp and Hp). Beyond that point is when you start getting upgrades. A mace upgrade for 5000 followed by an armor upgrade for 5000, beyond that I can only assume is upgrades for the rings.
