Lauscha

1. There are only 10 ships of the glass pirates remaining
2. The glass pirates are a people called "Lauscha" and they were saved by their god as their world ended
3. The pirates rob settlements because a new gos has offered to return them to their time, when they can stop it if they provide enought raw materials.
4. They once (two or three thousand years ago) lived at peace with the people around them.

Glass pirates are known as a race, Lauscha, a people who are their own phylactery. A divine moment as they were saved from a cataclysmic event on their own world. They were destroyed and their souls were fed into the crystals that make their bodies a glowing gem in the centre. They have been diminishing overtime as they have been unable to reproduce.
They are lead by Captain Ozarka Safeshard, a neutral being of the stars.
Their god who saves them drive them to the material plane as their place was destroyed.
Their new god, unnamed, orders sacrifices and promises to return them to their world right at the moment a decisions was made that could turn the tide. They prepare in war for this moment. They are building alters to the god and pouring what they steal in.
They carry around elaborate boxes, each with a gem that holds the souls of their fallen family.
They used to store them in a centralized place, but many raids and mishaps resulted in nearly a 10k deaths. One place remains but those who set it up volentarily killed themselves to preserve it until the new world could be found.