Code Vein: Decayed Ship Interior Walkthrough

Climb the stairs and take the card: City of Sacrifice from the soldier's body. 

Get down and up. There is an enemy at the top (another one will jump behind you as you get close) and a Rotten Mistle. To get there, jump down onto the platform.

When you reach the end of the road, turn left and then immediately right. The road leads to a hidden path where you will find a chest with Nightspear +3. Jump down and go back to where you came from. Awakening MJ109 and Blood Cartridge (x3) are on the left side of the cave.     

Go right. There you will meet an enemy with a shield - defeat him. Go down the stairs. You will meet a powerful soldier in white armor. After defeating this enemy, open the chest - you will find Raven's Fatigue +3, Blood Veil. Go a little further and take the regeneration multiplier (increases the amount of HP restored). Once you've collected the items, go back up the stairs.    

The red demon stands a little further. After defeating him, break the wooden boxes.

Jump straight to land on the ground. Be careful - you will face two opponents blocking the narrow path.

At the end of this path you will find the aforementioned Rotten Mistle. Return to the place where you encountered the red Lost. This time take the path to the left. There you will have to defeat several enemies. Choose an elegant fountain pen. Keep going forward. 

Stop at the location shown in the image. Jump down and go forward. The stairs are on the left. However, before climbing it, go a little further to find a chest guarded by an enemy. Be careful because this opponent can easily push you off the edge. Open the box and take the Broadsword +3. Now you can safely climb the stairs. Go straight ahead. On the left, there is a mini arena with three large enemies. Don't touch them now and go straight ahead. Keep walking until you see a ladder. Go down it. 

A red demon will stand in front of you, guarding the regeneration multiplier. Climb the stairs and return to the mini-arena. It is better to lure opponents one at a time than to fight three enemies at the same time. Defeat them and then take the Dark Seeker's Item Piece. Then take the other path and go down the stairs. Cross the narrow passage and fight one enemy. After a few steps you will find a rotten Mistle. Purify it and then return to Mistle at the Shipwreck.