an evolved burrower  

I had been checking for this mob to spawn for the last few days. It spawns at the end of the underwater tunnel which you can reach by simply heading left from zone in, and diving into the pool there. What others said is true - it begins in a larva worm form, and slowly grows into an enormous size before finally hatching into the Shik'nar form. In the last stage of it that I caught it up at, it was nearly as long as the entire room it spawns in!

Finally found it up today as the targetted version. The hatched burrower in Shik'nar form seems amazingly small compared to the large larva form. After a long 18 minute battle with it, I managed to kill him solo, as a L70 necromancer. With only 5% mana remaining, I dealt it the killing blow.

Most of what everyone else reported is correct. I parsed 148khp damage in the fight, of which a slight amount can be attributable to regen due to the long duration of the fight. 649 quad max hits on me with 1% shielding. It flurries, is permarooted, and it does summon.

Also, on a slightly humorous note, the instant the evolved burrower died, sure enough there was the tiny little larva form respawned under it again, so small that it could barely be seen. Very creative event and one of the best challenges i've come across. Good fun.