Pirates are humans similar to Buccaneers, but have clearly been lost to chaos and evil. Rather than simply self-interested, pirates are actively cruel and destructive, sociopathic, amoral, and contemptuous.
Large pirate groups are lead by fighters of significantly high skill, spread fairly evenly throughout the hierarchy. The pirate leaders occasionally work together with skilled wizards and clerics of deities related to thievery, violence, or bloodshed (the clerics tend to be a bit weaker than the wizards or fighters in the force).
Pirates outfit themselves well as warriors, with swords, shields, chainmail and leather armor, spears, bows, and crossbows.
Pirates dwell in their own ships, and rarely leave except to raid or plunder (or to hide). They keep food, drink, and captives in this location as well.