There are no lockout timers for this zone. You may re-enter over and over as many times as you like, until the door vanishes and you must find it again. The outside of the door will be guarded by a single tainted scorpion (38).
The entrance moves around the Defiled Forest. Known locations are:
Seems to be random whether you get a named, or none. In 20 runs I have seen all three of them, but never more than one per instance.