Your shadow and jewelry: How to gain jewelry for the shadow and is it worth it?
First of all, to get access to the instance you have to complete the quest : "Shadows in the Night" [8], once completed, you will get access to the instance.
The instance itself is not really hard, is just time consuming and requires specific shadow spell to manage to pass the doors, and the boss itself is much easier than what people usually expects.
Personally, i'd rather say that is not that bad of instance, is just time consuming and requires a couple of decent equipped shadow to manage to get out from the istance, and the reward is quite intresting, the more you level up, the more intresting the rewards becomes.
You can find a complete guide on the topic, both quest and shadow istance
HERE