How do I access the locked away chest at luppi ruins

[Kaiser Biggie]

There's a 3rd ladder luppi ruins at firlun that will lead me to a cell with a chest locked in a cell with a blue goblin, how do I access it?

[hcl]

not from my mind, but you could check at this wiki:
https://9d3.fandom.com/wiki/Luppi_Ruins

[[Mi.Sa]Skullduggery]

When in firlun go to the water to the west and hug round the walls of the building going south east the you should find a ladder going down.