Your strange team arrives at Sentinel Hill to discover that the goblin was right. However, Mortwake sees no issue with Sentinel Hill being burned down. He simply raises its slain guards into undeath and conquers Moonbrook while Kearnen shoots down the kingpin. He's even kind enough to leave behind some of his minions with commands to obey the Marshal.
When Sentinel Hill is rebuilt, it won't be quite the same, but it will be secure!