Shadow Nexus (Challenge) how to get there?

Hi.
Ive discovered most of the areas in "Realm of Torment" but couldnt yet find any way to the Challenge-Mission..."Shadow Nexus"..

Does anyone know which Area it is in ?

1)Nightfallen Jahai
2)Domain of Fear
3)Domain of Secrets
4)Depths of Madness
5)Throne of Secrets

and maybe from which point it is closest to there ?

any help appreciated . thx

Map to the "Gates Of Torment" and run around the outpost til you see the zone labeld 'The Shadow Nexus".