Detect Hidden 100
Hiding 100
Lockpick 100
Ninjitsu 110 You will often need to take the form of a llama for fast movement.
Remove Trap 100
Stealing 120
Stealth 75 it's enough to wear a medable armor (mage armor or cloth).
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The chest is hidden in such a triangle. the main thing is to find points 1 and 2 to understand which way it is directed from you. To do this, when you find one point, take a step back and try to step diagonally. If you step correctly, the second square will also indicate that something is hidden here.
(https://live.staticflickr.com/65535/54861401047_2f9c4affc7_m.jpg)