Spires of woe are a type of defense tower built by the Burning Legion. They were used during the defense of Mardum, the Shattered Abyss against the Illidari assault, and again a decade later at the Battle for the Broken Shore. They guard Nath'raxas Hold.
While at the Broken Shore, they were accompanied crystals which anchored the structures to Azeroth. When the crystals were destroyed, the spires crumbled. Destroying the crystals paired to the spires in Mardum, however, just disabled them.