The reconstruction worked flawlessly. The sigil can now be used to unlock the seal on Trollbane's tomb. Return it to Zengu, no doubt he has additional tasks for you to complete.
We're halfway to being able to remove Trol'kalar from Trollbane's tomb. We are not exactly sure where the third sigil is, as its holders seem to move around Arathi quite a bit, but I have faith that you'll be able to find it.