A secret boss, Ladon only appears on a certain level, if certain requirements are met and the level cap is set to 20 or below. You will require the blessed ring's "Soul Purge" skill in order to fight Ladon.
The stage is 巡礼の回廊, it can be any time of day. You may have noticed there are glowing orbs that you can strike within the level. If you use soul purge on these orbs, a miniboss (high class) will appear. There are four of them to be defeated. If you defeat all of them, the boss will change to Ladon. This is the best way to obtain 魔竜の眼. To be on the safe side, do not descend the stairs to the boss room until the level and midbosses are all defeated.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License