From the main road between J'Rais Bridge and N'Mar's Ascent, take the path east that leads to the owlbears. The spiders will be all along the road next to rocks, nearish ( -615, 30, 40 ) /waypoint -615, 30, 40.
If you speak to Zintra again after the quest is complete, she will ask if you want her to show you the results of the quest. If you say yes, she will apply the illusion to you, and you get an awesome drider illusion for a while.
The capitalization, punctuation, and spelling of the title of this article have been verified and are correct as-is. That is the in-game spelling on Test as of May 16, 2007. I have reported it.