This Friday (9/17) at 8pm EST I will be organizing a Tethra run for anyone interested in coming. I am generally looking for anyone with even minute interest in the mob. It should prove to be challenging even at 85 considering it's ability to grow in level but I am sure with enough people it can be taken down. If interested you can reply here or hit me up on game.
http://wiki.ffxiclopedia.org/wiki/Tethra