You can find the Void entre at coördinates (32,40) at the top at the stairs.
After that avoid being detected, after finish you will be transported out.
You have to disrupt 8 diff. activities in the void. what they r i dont know yet ran through once an didnt notice anything, will go look again .
Use portal to get to shadow side. Move around mobs ( don't attack them or you will be kick back ) and disrupt 8 Ethereal activities.
See My Video If need it -
Hidden in the Hollows Video
I had to go down the stairs from where the map showed the start point, partially into the cave itself. Around 33.59, 40.39. Just as the "Umbra Hollows" appeared in text on the screen for me. When I looked back up the void tear had appeared at the top of the steps.
For the World Quest - click the portal to "cross over". You'll see a bunch of glowy structures around the area, and they're pretty large so easy to see. They're also indicated on your minimap by a large yellow dot. Even though all the mobs show hostile, most don't attack. Watch out for the mobs with the symbol over their heads and don't cross in to the dotted line that surrounds them - those will attack. Click on eight different structures to finish the quest. You'll automatically be ported out when finished.
We thought ourselves to be save, that there is no way for them to follow us all the way to Argus, but we were wrong "AN ILLUSION? WHAT ARE YOU HIDING!" (A dissimulation? What are you concealing?).
Polymorph is your best friend as it will disable the humanoid sentries completely.
Of course work even with others forms of CC.
I gotta say, I really like a questgiver whose instructions are
"Disrupt their activities. Or don't, whatevs."
[Hidden in the Hollows]
[Enter the Void Tear]
[Ethereal activities disrupted]