The city can be reached either through venturing into the Abyss - the city is found near the portal to the Endless Maze - or by taking the portal within the Temple of the Abyss.
Broken Reach is a trading outpost and open for everyone to visit. Although Devils and Celestials are subject to racial abuse and should enter the city with care as the slightest discourtesy might get them dragged out of the city where Red Shroud's law does not protect them.
For the last 200 years, Broken Reach has been one of the closest things the Abyss has to a sanctuary for outsiders, a place where travelers to the plane can live and operate from without worry of violence, impressment, or enslavement.
Two centuries ago, the city then known as Bladed Reach, after standing firm for over 800 years as the gate-town to the Abyss, suffered a city-wide massacre, the causes of which are still unknown. Whatever set it off — and most assume tanar'ri instigation in one way or another — within a single day, nearly the entire population of 8,000 people was wiped out. Perhaps a few dozen survived. The event was so strong, Bladed Reach slid almost overnight, leaving the city of Plague-Mort in its wake.
It was but days before Red Shroud, daughter of Malcanthet, came across the ruins, following a period spent in Limbo studying the ways of chaos. It was here that she sought to first make a name for herself. Clearing out the other fiends squabbling over the ruins, she took firm control of the settlement. Gathering those that survived both the massacre and its aftermath, she began rebuilding the city as a fortress, keeping other fiends at bay while she called in any number of favors and allies to help solidify her claim. Attacks continued on this prize, for it still held the Abyss side of the new gate-town's portal. But her defense was quite solid, and within ten years, her claim on the newly-named Broken Reach was considered unshakeable.
Thanks to its connection to Plague-Mort, its status as gateway to the Abyss, Broken Reach quickly became a major trading hub on Pazunia, something that layer hadn't seen in centuries. Surprisingly to all, Red Shroud allowed free passage to merchants, traders, and travelers both into and out of her city. She outlawed violence within its walls, and barred the molydei from capturing any within for the Blood War. While not truly a safe haven, it was calmer than most any city to be known in the Abyss, and for the first time, to the frustration of many Abyssal lords, outsiders had the means to enter the plane and see it for themselves without needing to worry about being slaughtered the moment they stepped foot within its span.
In the modern day, Broken Reach continues its status as the hub of the Abyss. It serves as a libertarian paradise, with Red Shroud preferring to keep a relatively hands-off rule of its people, not even taking a title. The only rules she regularly enforces are the ones she made when the city was first taken — no violence, keep the Blood War outside, and ensure she gets a portion of all transactions. Disputes within the city are taken to her, of course, though as she is a tanar'ri, she can be quite harsh in her determination. Still, she holds firm to the belief that everyone should be free to do as they please without being repressed by the decisions of those "above", wanting her city to be a true model of chaos as self-determination.
Above ground, the city is little to look at. A few of the original buildings from the days of Bladed Reach still stand to some degree, though they have fallen into severe disrepair; for the most part, though, the surface has nothing but crumbling towers enclosed by a series of trenches, walls, and barricades; the defenses built on Red Shroud's order two centuries ago, improved and expanded since. Below ground is where most of the citizens of Broken Reach make their way, with the local residences and businesses, the city's arsenal, the food stores, and even the Reach's crypts all found in the network of tunnels that transitioned along with the rest of the city - expanded since as needed, of course. The portal itself is found here too, a sphere glowing yellow at the base of a roadway winding up, in a chamber below Red Shroud's palace that, when the need arises, can be sealed off with a 20-ton slab of basalt.
Although the majority of the city is below ground, there are two exceptions. First is the city's open-air market, a center of commerce that isn't rivaled on the plane outside perhaps Azzagrat. The taxes and levies imposed by Red Shroud do make goods here more expensive than elsewhere (most items are nearly twice what they would cost in a normal market), but few in the plane can afford to be picky. Most anything one would expect to find in an Abyssal marketplace can be found here, plus various extraplanar goods brought by the numerous caravans. The soul exception, unsurprisingly, is poison, the sale of which is strictly prohibited by Red Shroud. Not out of any concern of safety or decency, of course, but because she doesn't wish the competition.
Second is just above this: the palace of Red Shroud, the only new building above ground since the city slid. The massive structure, that allows her to oversee the whole city is held on pillars 60 feet above ground level and was designed by one of the preeminent Sensate architects of two hundred years ago.