You're likely deep into the late-game misery of Arche Abbey when you realize your inventory is missing something. It’s that nagging feeling of an unfinished questline. Specifically, the Rusty Cryptic Vessel Lies of P hides away in a corner of the world most players sprint past because, frankly, everything is trying to kill you at that point.
It's easily the most "out of the way" vessel in the game. You don't just stumble upon it. You have to buy it, but only after finding a specific expansion box. If you're hunting for the Black Cat’s outfit or just want to see every inch of the Barren Swamp, this is your ticket in.
Where to Actually Get the Rusty Cryptic Vessel
Most players think these things are always found in chests. Nope. Not this one. To get your hands on the Rusty Cryptic Vessel Lies of P, you first need to reach the Arch Abbey Entrance. Near the Stargazer, you'll encounter a heavy combatant—one of those large, club-wielding Alchemists. Defeating him (or just sneaking past if you’re low on Pulse Cells) leads you to a chest containing the Special Krat Supply Box.
Take that box back to Polendina at Hotel Krat.
If you’ve been keeping up with his inventory expansions, he’ll now stock the vessel for a handful of Ergo. Buy it immediately. Don't sit on it. Then, take it to Venigni. He’s the only one who can "decrypt" these metallic tubes of mystery. Once he tinkers with it, he hands you a deciphered note showing a locked gate in the Barren Swamp.
Cracking the Barren Swamp Secret
Remember that gate near the Barren Swamp Bridge Stargazer? The one next to the NPC Rookie Explorer Hugo? That’s where you’re going.
Before you have the decrypted Rusty Cryptic Vessel Lies of P, that gate is a literal dead end. Once the vessel is active in your inventory, the gate magically—well, mechanically—unlocks. This opens up the Hermit’s Cave.
It’s a gauntlet.
The cave isn't just a straight walk to a treasure chest. It’s packed with environmental hazards and those annoying, crystal-shuttering carcasses that love to knock you off narrow wooden beams. Watch your step. The verticality here is a death trap if you're impatient. You'll need to navigate several levels of scaffolding, dealing with traps and elite enemies that have way too much health for such a cramped space.
What’s at the End of the Tunnel?
At the very back of the Hermit's Cave, you'll find a safe. Inside is the real prize: the Black Cat's Hunting Apparel. For players invested in the lore of the Black Cat and Red Fox, or those who just want to look like a high-fashion feline assassin, this is the only way to get it.
You also get a Quartz.
In Lies of P, Quartz is king. You need it for the P-Organ upgrades, and by the time you're finding the Rusty Cryptic Vessel Lies of P, those upgrades are getting incredibly expensive. Finding an extra Quartz tucked away in a secret cave is often the difference between getting that "Retain Guard Regain" upgrade or dying to the next boss’s fury attack.
Why People Miss This
The game doesn't hold your hand here. If you don't talk to Polendina or check his updated stock after every major boss, the supply box just sits in your "Bag" tab gathering dust.
Also, the Barren Swamp is a nightmare. Most people finish the boss there, see the "Green Monster of the Swamp" go down, and never want to look at a patch of mud ever again. Returning there feels like a chore. But the Hermit’s Cave is actually one of the more unique mini-dungeons because it’s purely optional. It feels like a classic Dark Souls secret area.
The lore implications are subtle, too. It connects back to the Red Fox and Black Cat’s journey, giving a bit of physical history to the characters who have been following (and occasionally betraying) you throughout the game.
Actionable Steps for Your Playthrough
If you're currently standing in the Hotel wondering what to do next, follow this sequence exactly:
- Check your Supply Boxes. Ensure you’ve delivered the Special Krat Supply Box from Arche Abbey to Polendina.
- Purchase the Vessel. It costs 1,000 Ergo. Pocket change at this stage.
- Talk to Venigni. Do not go to the swamp yet. He must open it first.
- Warp to Barren Swamp Bridge. Face the gate where Hugo stands.
- Clear the Hermit's Cave. Bring fire damage. The carcasses in there are weak to it, and it'll make the elite fights significantly faster.
- Open the Safe. Don't forget to equip your new threads and slot that Quartz into your P-Organ immediately.
This quest is easy to fail simply by forgetting it exists before you trigger the final ending sequence. Once you've beaten the final boss, you can still go back and do this, provided you haven't started New Game Plus (NG+). However, having that extra Quartz for the final stretch of the game makes the endgame bosses significantly more manageable.