This is the "scarce" elemental spawn for the Tenaro "hidden" quest. If you're doing this quest be sure to get the earth elemental as soon as it pops. Only one spawns at a time and its uncommon. I've been finished with the other 11 kills (3 ea water, air and fire, and 2 earth) and have spent the better part of 3 hours, on and off, logging in to try to kill the 3rd and final earth. I'm passing the time root-rotting other trash in an even-more-hopeless quest to get an augment.