Jack Rover - The mysterious crystal

Hi, my name is Jack Rover. Till recently Ive lived my life in peace. I travelled the world, sometimes got into different fights and awkward situations, in one word didnt really care about anything. Well, what to say, I am proud to be a pirate, and what pirates are? We are too arrogant and too careless especially when it comes to the things left unattended. So at one usual (for a pirate) day filled with rum, troubles and cannonades, I accidentally found a strange piece of paper with various marks...