After taking Herewaruk's soul and body, Ed didn't dare stay.
'Nobody else should be coming in here' He would take his time to analyze the arrays and examine the knowledge at a later time. Priority lay in saving his orcs.
Ed left promptly after thinking so, only taking the liberty to block the hatch on his way out. There was a chance that a secret tunnel existed but he obviously wouldn't take the time to find it.
'I need to hurry' That was the main thought that plagued Ed's mind. Realistically, there was no reason for this.
He had only bonded with Sharog, knew the name of Nag, and lost pretty much everyone else. Why did he care?
Was it because he was making a city, or was there a hidden reason? Did he want their souls perhaps? Did he want the manpower?
It didn't matter. What mattered was that he wanted to save them.