"Grab the Witcher set diagrams, then go through the doors the statues unlocked and keep your eyes to the south-west to find an Aardable wall. Blast it, then search the cavity beyond to find a chest containing the silver sword “Loathen” ."

First of all, there will be Nightwraith here, and the loot in the chest seems to be random (not a single sword in my case, but some relic armor).

"Remember, you can only use these if you have caught the previou version of the items, which you can read more about on the Temple Isle quest."

In this quest is only Part 1 and Part 2, But you also need to complete Part 3.

"Objective: For defeating Jutta"

It is from previous part.