Wake up to your crew panicking before you make your complaint known and you head off.

Follow the footprints to the Hoodoo House before facing against Old Scratch. Target him alone and let the rest be collateral damage. Find the Grave you're looking for before leaving to catch up to Ratbeard. (You will gain Old Scratch as a Companion)

Take off for Bounty (Treasure) Island and solve the puzzle. Once you get into the hole, fight off the baby crabs and let Old Scratch do some voodoo.

Make your way to Waponi Wu and climb the volcano. Be careful of the lava fish and use your far-rangers/casters to their full extent. Once you get to the top, Chumba Wumba and Lord Nightshade will be waiting. If you chose Ceren or Duncan, then they can help you set up your teammates. Ceren will have the advantage against Nightshade while Duncan will have powerful attacks that'll pierce through their defenses. Nightshade will fall easily, but Chumba Wumba will rise again. Ratbeard will advise you to go for the three totems. If you focused yourself and your wizarding choice on the bosses and had your other three crewmates heading for the totems, then you'll be good. Slam hits against the three before finishing the battles. Go through the cutscene before grabbing the gold and a mysterious package. Then head back to Avery (You should've gained Ratbeard as a Companion).

Get back and give Avery the chalice he was looking for. Make sure Ambrose gets the package. You will be given a chance to rest afterwards. Though you'll pass out when you reach the dorms.