Story to Unlock Secret Merchant Shop in Elden Ring

First, you have to go north east towards the river.

And find a spot to jump down a cliff to the river.

You need to wait for bloody finger nerijus.

Keep distance, and use the long weapon hits (R1).

Bloody finger hunter Yura will summon.

You have to hit, dodge back away, then hit, and repeat.

Helper summon will arrive soon.

You don't have to attack the helper, kill Nerijus.

You will get Furlcalling finger remedy and Reduvia.

You can see Reduvia stats and move sets.

After that, enter Murkwater cave and touch the grace.

Go deep into the cave and enter the right hole.

You will need to traverse the mist and open the chest.

And wait for a fight with patches.

You have to dodge, keep distance, and use long weapons.

Hit R1 once, then dodge away, and repeat.

Keep distance, damage him to half HP.

If he says wait, then you don't have to attack anymore.

Wait for enemy felled message.

Keep talking by using the triangle button.

Once he is repeating, you have to exit the cave.

Then go back inside to his location.

He is now a merchant, you need to talk to him.

Ask about bandits and chest (optional).

He sells some very rare stuff.

You must get a cookbook and margit shackles.

After finishing, you have to open the chest nearby.

And get teleported east to a bear.

You will need to summon rotten stray.

Wait for him to bite him to start rot.

Keep distance hit only if safe.

Once Scarlet rot has started, just wait.

You have to keep far away so that he won't attack.

He will eventually die from Scarlet rot.

You will get beast blood and fold tinged excrement.

After that, you can sleep at any grace and teleport back.

He is still selling to you.