a) Sit tight and hope to hell there is a rescue on the way. I mean, at least some of the Rangers must have escaped, right? In the confusion of a second attack, it will be easier for you to get that sceptre piece before fleeing.
b) Wait until the necromancer and his pirate crew are asleep. They're human; really disgusting, but still human. They'll have to sleep sometime. Then sneak the heck out of there with the sceptre piece. You'll have to leave Hessa behind, but the sceptre is more important.
c) Wait until the necromancer and his pirate crew are asleep, then take Hessa and attempt an escape. Now that you know what you're dealing with, you can regroup and find a better way to tackle the necromancer and his Red Band and retrieve the sceptre piece.
Vote! Share! Good luck!