It's the most complex of the Elemental Blade quests, thus easy to miss it first time through.
You wouldn't believe how many people leave the Shadowmire without the Earth Blade!
Then the question, "can I get back in to get it?"
Fortunately, that's close enough to the beginning that it's an easy restart.
There's a glitch that sometimes happens in the game where General Dehrimon doesn't give you the Kragmor quest to kill the Wartok chieftan Snotmaw.
That's a problem if you want to get Mournbringer, also.
Similarly, (after defeating Maulgak in the North) if you aren't terribly intrepid, and fail to backtrack, you could miss the Ice Blade...
Was this your first time through D:TAG?