User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-3146930-20130720154210/@comment-3146930-20130721122619

But what qualifies as underground? I mean when Percy fell into a sinkhole in Alaska, Hazel wasn't able to pull him back up even if he was surrounded by mud and dirt. Yet back in Camp Jupiter, she was able to use a shallow tunnel to reach the enemy base in the War Games. I mean Nico calls rock up from the Underworld, so could Hazel call dirt from underground to the surface and control it?