I just wanted to mention that the rats in this area (about 20 of them together) have an insane spawn time - I was unable to kill all the rats despite chain casting of high level area effect spells - they would immediately repop. SOE has nerfed the value of the plague rat tail, but you can still collect tons of rat whiskers here.
Takes me about 2 hours to fill a backpack with 8 stacks of the whiskers. Turning them in to exterminators in the various cities is superb for factioning. You'll make a small bit of money too.
I would venture to say that this is the best place in the entire game to farm rat whiskers. To get there, when you first zone into the warrens, go RIGHT, follow the tunnel to a wooden door. go in, and explore. soon, you'll see the rats.
Btw, the frenzied rats have undead aggro, but not the trained rats.
Edited, Jan 10th 2007 10:38pm by zirumkin