The Abyss has a lots of gorges, chasms and geological gaps, waiting for unwary travellers. There is one particular gorge, though, that is known among practically all Abyssal denizens: The Chasm of the Lords.
There are few physical attributes to describe the chasm: It's a large gap in the earth, somewhere between hundred and thousand yards wide, a few miles long, and infinitely deep - or at least, it seems like that.
The obviously curious thing about this gorge is that it moves from place to place. Not by standing up and walking away, mind you, but by closing the gap until only the normal landscape remains - while simultaneously, the chasm re-appears on a random place in a random layer.
Of course, with a name like that, the Chasm of the Lords has a few darks as well. First of all, rumour has it that with every jump to another place, whether on a different layer or realm or close to its original location, the Chasm creates a spiritual connection to one of the Abyssal lords - and cuts the previous connection.
What exactly the effects of this spiritual connection are is unknown, but most assume that everything falling down into the Chasm ends up whereever the connected Lord wants to have it. Some say that the Lord can populate the Chasm with his minions, easily gaining access to foreign layers, sometimes even to the realms of his direct enemies.
As the Chasm of the Lords is (usually) open for the local residents to explore, many tanar'ri and other Abyssal creatures have set up kip in the Chasm. Most of them stay only for a short time, waiting for the Chasm to appear in a place they like better than their previous home. Others create a permanent living place, mostly in the Chasm's upper regions. The lower regions are sparely populated, but the farther down one gets in the Chasm, the more powerful the residents become. Going down about a mile, travellers meet few other creatures than true tanar'ri, retrievers and the like.
Strange enough, many tanar'ri seek the Chasm, risking their very life to go down as far as possible. It seems they know or feel something about the Chasm's nature, some dark unbeknownst to mortals - and they seem unwilling to share the secret. Of course, this doesn't keep them from forcing mortals (and other beings) to accompany them - as cannon fodder, mostly.