Mugwort
The first time you enter Beetle Forest you encounter Koris, who offers to train you. Koris presents you with a healing item known as a Mugwort before giving instructions. Koris makes you start over if you disobey his orders, but he doesn't take back the Mugwort. Start the process over and Koris presents you with a second free Mugwort. Keep doing this trick over and over until you reach your item limit of 20.
Eternal Corridor
After completing the game, save your game and then resume the saved game to access the Eternal Corridor, an extensive line of corridors containing new monsters, new mini-bosses and even minion skins that let you change the appearance of your monsters without altering their abilities. You won't be able to save between corridors, so be prepared to explore as long as possible in one sitting.
View Secret Minions
Bring up your list of minions on screen and start the merging process. Select the first minion you want to merge and then go to one of the blank spaces and select it to view the minion. The screen displays a secret minion. Repeat this process to see multiple secret minions.
Minions
Raise your Minion Capture Level above 30 and you'll be able to capture minions without engaging in battle first. You'll also have the ability to grow minions as opposed to merely merging them. Take your time and train the minions, letting them grow and reach their full potential before merging them.
Fire Boss
You encounter the Fire Boss on your second trip into the Beetle Forest. Make certain you have at least one water minion with you that possesses a powerful water attack, like Vahlia, at level 14 or higher. Bring more than one water minion if possible, because the Fire Boss won't be easy to beat.
Earth Boss
To defeat the Earth Boss, use air minions with powerful air attacks to do the most damage. Avoid using merged minions whenever possible. If you have to use merged minions, make certain the minions contain only one element and that their family history features no elements other than the element you're using to attack the Earth Boss.