How to reach Chelsith Reborn
Unless you have completed the Portal Attunement quest for Chelsith Reborn you'll have to take the long route to this zone. First, let's start in the Guild Hall since that's the most diverse portal locations we all have access to. Purchase the Shadowed Sand of the Twilight Sea and head to Twilight Sea (shown in the map location above).
From the Twilight Sea you're going to want to run west to The Scarlet Desert. The zone line is a short way away. Once you reach The Scarlet Desert you'll want to continue west until you reach The Grey. This is shown on the map below.
After you make it through The Scarlet Desert and to The Grey you'll be able to see Chelsith Reborn's Fear Crystal on the map in the upper left corner. So basically you're just gonna wanna run west even more until you reach our destination.
The fear crystal, the thing you need to click on in order to zone into Chelsith Reborn, is a large purple crystal in the center of a lake. It's shown in a screenshot below.