Donce
07-05-2018

Plundered from Minotaur in the Labyrinth 10th floor. Part of the memorial album "Proof of Mythology (No.1)"

Guilder
03-27-2019

As Donce sayys, this is part of the Proof of Mythology (No.1) Memorial Album. This item drops randomly (and at times, rarely) from the mighty Minotaur, rumored to lurk deep within the Labyrinth endless dungeon.

You have a chance to run into this foe every 10 floors, but it's quite rare -- the Seeker of the Unknown title may help you find the Minotaur more frequently, though not by much.

At the very least, we know the B10 version can drop this item. Whether or not its more powerful variants deeper into the Labyrinth do so as well remains unconfirmed at this time.

Regarding the item's effect, you're probably better off using Swan Feather Pen than this, but it can be fun to hunt for I suppose. Happy mythical monster hunting to you. Cheers.

Guilder
03-27-2019

Oh, right. For what it's worth, JP wiki suggests Minotaur floor 10-40 versions have a chance to drop this. Your mileage may vary -- the JP wikis aren't always accurate compared with international servers.