Old Cryptic Vessel is a Cryptic Vessel in Lies of P.
Location[]
The Cryptic Vessel is located in the Barren Swamp Bridge area. From the Stargazer, speak with Rookie Explorer Hugo who can be found beside a closed gate that leads to Hermit's Cave. After speaking to him, he will give the player the Cryptic Vessel.
Description[]
An encrypted storage device in the shape of a metal cylinder. Venigni might be able to decode this device if you ask him.'
The storage devices that hide secrets using encryptions were popular among the Krat upper class. Naturally, the decoding devices targeting the rest of the population were also popular, but most have been destroyed.
Decryption[]
Take the Cryptic Vessel back to Venigni at Hotel Krat to decrypt it. It will show a picture of a slum shack in the Path of the Pilgrim. Travel to the area's Stargazer and take the lift down if the shortcut was unlocked. Next, follow the path to find the shack in the photo on a hill. Speak to the Slum Resident to obtain the Robber's Shack Key. Afterwards, use the key to unlock the nearby shack. Upon entering, the floor will cave in, revealing it to be a trap. Deal with the enemies and then go to the end of the basement and then climb up two ladders to return outside. Go back to the shack, being careful not to fall back down, and open the chest to obtain a Legion Caliber and the Life Amulet +1.
Transcript[]

Order: An old shack in the Tomb Slums in Malum District. Look got the bleak tree and laundry line and enter the shack next to them.
Appendix: An agreement is attached for mutual trust.
I kept hiding the stolen goods in the Barren Swamp and realized something. Ah. I'm never going to return if I keep going to the swamp. All I've known is the life of a thief, but I don't want to die now.
So we're retuning to our sweet home. Even if the Black Rabbit Brotherhood is making trouble we were technically before them in the Malum District. In the slums, you follow the slum rules.
First, bring the stolen goods to our old base. We may be dumb, but we're loyal, unlike the rich. Here's to a lifelong friendship.