So aside from the complaints about the coins vanishing, it'd be nice if we could rearrange the keys to suit our personal preferences. For example, it would have been easier for me to play if the Items and Spells keys were switched. Anyway, still enjoyed the game and I'm hoping to see more games from you like Siegius (or just even based on it, like this one).
Neraine, Beelzebub
Primary Agility, Secondary Stat should be Power, Tertiary Stat is Endurance
Use Feather Boots and Deep Blue. At lower levels, use Azure Dance as your primary weapon. But once you've maxed out Agility, you should only use Azure Dance for small and medium enemies. For the larger ones, use Crystal Dust.
You won't regret it! With this build, I've managed to keep a lot of the bosses frozen throughout the battle. Don't be afraid of using Swarm Heart twice at the start of a boss battle, and as soon as you can, summon a third hive.