No, not the Nar one, the drow one, from Drow of the Underdark.
It's a prestige class for Warlocks. Other than fairly easy skill reqs, the class requires drow as race and alignment as chaotic evil. Drow would suck if there wasn't an LA 0 drow racial class in the back. You can even take a level in it whenever you want, get a boost to int and cha, then buy it off, and forget about the rest of that craptacular racial class forever.
All you really need is one level of Demonbinder, as it gives you class lvl + cha modifer demon binding points and the ability to bind everything from dretch to balor at the first level of the prc. When bound to a fiend, you get some temp HP, resistances, and the ability to spend a point as a swift action to do something that is ok. You also get 100 feet of telepathy.
The marilith bind is particularly attractive, as it lets you spend a point to eldritch blast as a swift action.
Binding a fiend takes a full round action and lasts 10 rounds. Points replenish after 5 minutes of rest.
The rest of the prc levels progress invocations known, damage resistance, and eventual electricity immunity. I don't think progression of invocations would actually boost eldritch blast damage, unfortunately. Which makes more than a dip in this class unattractive.
So, is it kind of like a weak version of sandshaper for the warlock?