Crabs Versus Skeletons automatically enters your journal once you have traveled deep enough into Black Cove, the pirate cave found on Cyseal’s beautiful and bloody western beach. You need a keen eye to complete this quest.
As with my other Divinity: Original Sin quest or puzzle guides, spoiler markers (—) for those who just need a nudge in the right direction are in key segments of this article. If you feel you’ve gotten all the information you want or need to progress, do not read past the (—) marker.
This guide assumes you have defeated the Source Abomination that spawns at around the same time the quest is triggered, so our adventure begins in the room just behind our now-dead lobster-clawed friend.
Be sure to grab whatever loot you can find in the room, then adjust the camera angle as seen in the image below to see the lever.
Pull it, and the painting on the wall will move to reveal a switch. Press the switch, and a hidden hatch becomes visible in the corner as seen here.
Make your way down the hatch to continue.
Which switch is the right one?
After making your way down the hatch, you will come to an area with several switches with odd names and an ominous-looking skull. This is one area I got stuck on for more than I would like to admit, and it’s possible you’ve gotten stuck on it too. There are so many switches, and only one will lift the skull for you to proceed.
The switch you are looking for is the Blood Stained Switch, which is just to the south the arena with the giant skull, hidden behind a cluster of ferns.
Behind the giant skull is a battle against the skeleton pirate Pontius. Defeating him will complete the quest. Be sure to pick up all of the loot he drops, especially the keys. One opens a chest on the ship in the room and the other is needed to open another door in Black Cove.