In early Kunark, there was a certain spot in the Field of Bone, a spider cave, that had a nice little gem. You had to let one of the spiders beat you down to almost dying, and a level 50 Earth elemental would pop up and become your pet, instantly killing the spider. I can't recall if the spider had to be a special one, I want to say it had a different texture than the rest.
I abused the crap out of that one, got my Iksar Monk to like level 25 in a day with it.
Edit - Found it on Alla's. It was the burynaibane spider, per this post:
http://eqbeastiary.allakhazam.com/se...&page=3#m15281