None know exactly how long ago the Corsairs formed, but it is generally agreed that they were once a group to contend with in the distant past, a strong united front of independant companies under a single banner. They were known to terrorize the shipping lanes of the Imperium, with crews made up of cutthroats that rarely gave quarter, and garnered a grisly reputation before they ultimately went into decline with the improving efficiency of the Imperium's Navy.
Popular rumor suggests that the Corsairs main base of operations was the nameless island where Croper's Cove is located, giving credence to the legends of buried treasure while similarly proving how stupid the idea of buried treasure is. Many dismiss this as a rumor simply because the Corsairs were too smart to bury their lucre in the ground, and a few believe they might have actually based themselves on Urk ar one point, it being inaccessable and generally unpleasent enough to deter any visitors. If they yet exist today as a hierarchy, then their headquarters are unknown.
In the early 1700s, several corsairs claiming to be among "the old guard" appeared in Imperial waters, and made a habit of targeting Naval vessels, specifically the flagships. Though a small armada, the pirates were able to create enough of a stir that the Emperor ordered a countermeasure, and in a pitched battle with the Imperium's finest ships the pirates were either sunk or scattered.
Today, some pirate ships still fly the colors of the Corsair fleet - the skull of a walrus set over a snowflake, the shape of which varies depending on who made the flag - though most think its more symbollic than a sign that said pirates operate at the behest of the Corsairs. However, in the aftermath of the conflict with Maelstrom and the recent expansionist efforts of the Imperium, pirate activity has been on the rise. And more and more, the jolly roger bearing the snowflake mark has been flown from the masthead of a number of barbarous vessels, many of which feature surprisingly improved siege weaponry.
The Corsairs have always followed a loose piratical code of conduct that draws from power held by the many rather than a single ruler, in direct contrasts with the Imperial regime. Overseeing the Corsairs is a "council" of powerful and charismatic pirates, known as the Patch. The Patch manages the operation of the Corsairs, keeping things in-line and ensuring that the pirates under them get the most out of their raids in return for a small cut of the spoils, as well as settling desputes and organizing effective sea-routes. The Patch's number is never set, but historically has averaged between 3 and 5 beasts. They often take their titles and roles in a mockery of naval formality - thus, one pirate in the council might be known as "the Bo'sun," and another "the Quartermaster."
Members of the Patch hold their posts as long as they like, though can be booted off by popular vote. They usually use a combination of respect, diplomacy and intimidation to hold their own, and only the toughest hold any position in the Patch long - assassination attempts happen at least once a day, and the Patch are always watching their backs.
Other than the Patch, the rest of the Corsairs are managed in whatever way they please. All sorts of cutthroats, brigands and high-seas robbers with their own methods and tastes rally around the Corsair's flag.
Though many varying kinds of sailing craft have been known to sail under the banner of the Corsair's, one legendary ship in particular is often mentioned in the lore surrounding them. Known as the Brinehammer, it is supposedly a massive, ancient vessel, easily as big as a man-o'-war, if not bigger, composed of parts stripped from sunken warships. Though a stout and heavily-armed ship, what strikes fear into the hearts of sailors is the sight of its ghastly figurehead bearing down on them: an ancient walrus skull, its ivory tusks cracked and rimed with salt. It is said that from this gruesome ornament the Ivory Corsairs got their name.