Temple of Shar is the location blocked off by Early Access ending in the underdark.
Mind you - you can still GET to that area by being a super big brain. And abusing reviving mechanics. But that'll just get you to an unfinished temple of shar area where most enemies are without equipment, some in odd areas and the terrain isnt entirely finished. There's like.. 1 conversation there. So I wouldn't recommend going there.
