The Rathe Mountains is an enormous and dangerous zone. It lies along the southern route from Freeport to Qeynos. The high peaks hide away many separate areas within the zone, each with its own dangers and things to discover. I think that the Rathe Mountains is generally considered just a confusing place to travel through, and not a place to adventure (at most, I've seen one person other than myself there).
This zone has many dangers in it. First of all, it is a mid-level zone. Although the region to the north of the entrance from Feerrott has many fire beetles to hunt, there is a great deal of overlap, and I've seen skeletons and lizard men roaming the area as well. Most of the other monsters were either gamble or tombstone to my 10th level ranger, or were in camps with two blues and an even, for instance. There is not a great deal of hunting if you are a solo adventurer here.
The monsters here are very powerful. There are Hill Giants and Giant Skeletons roaming some of the western parts of the zone, and Cyclops in the northwest. Many of the undead temples are covered with powerful undead, including the Dry and Ice Bone Skeletons and Giant Skeletons, as well as some named creatures I didn't get a chance to view personally. Combine very powerful with the fact that they are almost always in a camp or around others of their kind. If you want to take on one, be sure you can take on more than that as well.
The other danger, and this applies more to the evil races, is that everything here will attack you. There is a camp of paladins that will definitely come after you. I also assume the protected temple's guardians will come after you as well. Add to that every monster, and you've got problems.
Here, I will discuss the different areas within the zone and the benefits of each. To the south of the Feerrott entrance lie two lizard men camps, and a pair of 10th level characters could easily move between them. At 12th level they could move on to the orc camp as well. The two undead areas, though, seem to be much more dangerous. To the north of the Feerrott entrance lies an open area that is crawling with fire beetles, and the occasional low-level lizard man scout. There is also a high level orc camp. Nobody at the paladin camp would speak to me, but the gypsies and the Inn are very helpful.
Further to the west lies the zone where the hill giants and the giant skeletons live. If you can take them on, this area would provide good hunting. There are also guards that roam this area, although I have never caught one to try and speak with them. North lies a temple to some evil god (I assume) that is well guarded (the shaman has a pet). There is also a lizard man camp that could be taken on by that pair of 10th levels.
In the northwestern corner is the only readily accessible place to hunt bears for the evil races in the south. The problem is that for every brown bear, there are a bunch of grizzlies and kodiaks running around, so it's dangerous to hunt here. There are also protectors from the nearby temple that I believe will attack you, including one "unkempt protector" who roams the area. There is another high-level orc camp here as well. In front of the Lake Rathe entrance lies a creepy area with the hill that reaches for the clouds. Roaming this area are cyclops and giant skeletons, and the only gypsy camp that sells combine weapons this far south.
NOTE: Although the sphinxes were part of classic, they had no in-game purpose until the (un-classic) Beastlord 1.5 epic quest, and so on Project 1999 they are purely decorative.
The Sphinxes are the most unique part of this zone, and deserve their own section to discuss what I know and what I've guessed on their nature. I've heard that they are both extremely powerful (level 50) and that one is good and the other evil. Their names are distinctive and are linked with the named beetles in this zone through the first syllable (Zaza or Ankh). The temples that the beetles guard are remarkably Egyptian appearing, as well.
Now, what I've heard is that the northern sphinx (Ankh) is the good one, and the southern (Zaza) is the evil one. When I went to /con them, however, they both were ready to attack me. This leads me to wonder why that was, and why the good one would want to attack me (a wood elf ranger) and I think it might relate to my fight with the named beetles (Ankh). These beetles initially /con'ed indifferent to me, so I approached one and tried to hail it. It attacked me, and I had to fight off it and its companion. After killing them, I lost faction standing with the Stone Hive Bixies and gained faction with the Guardians of the Vale. Of note, killing Crushbone Orcs causes the same faction adjustment. I was led to believe that they were evil beetles from this, but if they are linked by name to the northern sphinx, and he now wants to attack me (like the beetles, now), then maybe he is the evil sphinx. This obviously warrants further investigation, and I'm very tempted to kill the Zaza beetles to see what faction that gives me, but I don't want to burn all my bridges. Any info on this would be appreciated.
Traveling To and From
On the middle of the eastern edge of the zone is the entrance to The Feerrott, the home of the lizard men and the ogres, as well as the temple to Cazic Thule. By following the path west and taking a northward turn at the temple guarded by Ankh beetles, you reach the northern corner of the Rathe Mountains.
On the western edge in the northern part, tucked away in a corner, lies the entrance to Lake Rathe. Getting to this can be tricky, as gypsies (who apparently hate evil races) lie at the entrance to this valley. The entrance also blends in to the surrounding area, and could easily be passed without noticing it.