In Athens, enter the building at (X:1590, Y:1258). Go into the next room and pick up the books next to the villager.
Move to the bookcase left of where you picked up the books, and click on it. An underground passage will open.
Enter the opened passage, and attempt to open the treasure chest, you will be attacked by a giant spider (Spider Monster, Lvl: 120, HP: 15000, Earth) (Land Spider, Lvl: 66, HP: 500-600, Elements: All) *4 (2 more spawn)