Crabs Versus Skeletons is a quest in Divinity: Original Sin. In the Enchanced Edition it has been renamed Into the Dark. This quest is essentially a run through the Black Cove. The quest is obtained when you come across a dying orc just down the start of the Black Cove.
Walkthrough
(Getting to the Black Cove) Head through the Western gate directly West of the Cyseal Harbour Waypoint Portal. Head North past the dead orcs, then West past the crying orc from The Grieving Orc quest and North past the minefield of traps.
Grulbarg the Fearsome and his troops
There is an orc miniboss called Grullbarg the Fearsome guarding the entrance to the Black Cove. Kill him and enter the Cove. You will gain 6750 XP for this battle.
Head East into the dungeon past the dying orc. There is a fight between Orcs and Skeletons here. Join the fight if you want the extra XP (10695 XP actually) or you can kill the survivors. You could also completely ignore them. We will be back here later.
Continue East, disabling the Poison Cloud traps and take out the Abomination mini boss. Enter the room East of the Abomination for the Another Crazed Mage quest.
In the room North of the Abomination, pull the level and then the switch behind the painting. This will reveal a trapdoor that you must go through. But first, you might want to head North to collect the quest Headless Nick and some loot.
Head East after entering the trapdoor and face a handful of crabs and traps. The key to the locked, unbreakable chest before the first bridge can be found behind some rocks by a shipwreck to the Northwest. Continue East until you get to the room full of switches.
Source Abomination
For some extra loot, drop a Teleporter Pyramid here and then trigger the 'Ominous Switch' along the Western wall. You may need a few points in perception to see the switch. The chest is hidden in the foliage. Teleport back to the switch room when you're finished.
Head East and up some stairs, you will find place full of triggers. You need to trigger the 'Blood-Stained Switch' to the Southeast of the stairway, hiding behind some bushes, to open the path. This updates the quest for 840 XP.
Head through the newly opened door and face and kill Pontius for 5550 XP and +1 Reputation. This completes the quest.
Grab his key and open his chest on the ship for a Bloodstone.
Use the stone if you want to unlock another room in your Homestead or save it for An-A-Mount Of Healing Magic quest.
You will also want to head to the scene of the fight between the Orcs and Skeletons to open a locked door with your newly acquired key. This route contains a miniboss and it is related to Kitty Love and Lost Love at the Lighthouse quests.
