Pontius Pirate is one of the bosses in the Black Cove.
Pontius' LocationOnce you enter the stone shelter, behind the Source Abomination, you'll see a lever in the right corner, pull it to reveal a button behind a painting. Once the button has been pressed, a hatch appears in the corner by the far door.
Once through the hatch you'll weave your way down some paths, fighting a few crabs along the way. You'll come to an open area with a few switches lying around, where you can also get the following achievement:
Down some stairs and hidden in some bushes you'll find a "Blood Stained Switch", press it and the big skeleton door back at the open area should have opened.
Fighting PontiusObviously strategies differ for each player depending on their party. The fight is made up of skeletons, so try and use crushing damage and fire.
Pontius' Death BlasterOn the ship behind the enemies, you'll see a pretty big device. This is Pontius' Death Blaster and is VERY useful, if you know how to use it.
Using the blaster took me while to get my head around but I hope this method works for you. The gun will fire in the direction your character is standing when you use it. There is a delay after you activate the gun, so this is the point when you use your remaining AP to step out of the way! Otherwise it will pretty much one shot the character who activated it. The blaster creates a massive amount of fire damage in a large AoE. I managed to take out most of the skeletons adds with a good aim. Allowing my party to focus on Pontius with little distraction.
You can also sneak onto the boat before the fight even begins and shoot the blaster on the first turn. I think it takes 6AP to use and I had 1AP to step out of the way, which worked fine.