When you get to the level 37777 map, where the map tiles are split up into grids. Rather than fighting the boss, who is in the centre of the screen, activate one of your bonuses. Equip some +encounter rings and search every tile until the bonus reads "?!" Fight on that tile and you have a chance of encountering a door enemy with what looks like outer space on the other side. When you beat this enemy you will be teleported to a new area, here there are a few extra "bosses" in the form of a crystal. There is one for each colour that corresponds to each stat: HP, ATK, DEF, AGI AND LUC. These enemies are tough, to consistently beat them you will need around 150k health and def, 100k agi and 200k atk. (With a recover necklace) Each one has a chance to drop a stat gem of it's colour of +4 or +5. +4 is only slightly better than the best you can buy, but +5 is significantly better. For example, HP +5 gives more than 100k health. A luck stat of 8k doubles your chances of getting an item, 34k triples your chances.