How do you progress world level, and what does it even do? lol
As a side note, I've gotten to the desert, but I still can't use teleporters. pls halp
You progress World Level by releasing nephs from your barns. Traits, trait level and character level define how many points they're worth. What it does is what asking the Emissary to increase trait level used to do in older builds.
Basically, it makes higher quality nephs (better than common) more likely to spawn with more traits and higher trait levels.
At maximum WL, you'll be finding Legendaries and Uniques more frequently than common types.
The teleporter is opened by talking to the Lamia you find in the desert. She should be in the same part of the area as the Harpy (Kestrel) spawn. Find the Kestrels and then turn 180 degrees. She should be there. Talk to her, then have sex with her.
This simple act of hedonism unlocks the ability to unlock the portals in the other areas you've been to.
Now when you want to activate a portal anywhere else, you just have to fuck her again.
Opened portals stay opened so you can just go anywhere that has an opened portal.