Here's the basic infomation we have on the chapter:
The Ivory Huntsman were once Night Lords who many millennia ago went their own way, considering their brother Night Lords to be little more than gaudy, lowbrow rabble. The warband isn't a centralised force, with countless smaller warbands or even lone marines travelling the galaxy, searching for the one thing the Ivory Huntsman value more then anything; a worthy prey. Every few centuries, the Ivory Huntsmen will return to their main headquarters, the vast Space Hulk known as the Heart of Darkness. This is called the (we need a name for this get together). The gigantic structure is vast in size, decorated in finest pine and fully furnished with everything the marines desire. Mile-long hallways are filled to the brim with the countless trophies the marines have taken, be they mounted heads or priceless portraits. Other parts of the Hulk are dominated by lounges, bars, libraries and other rooms.
When the warband meets aboard the Heart of Darkness, heretical scholars and noblemen are given a chance to go on board the Space Hulk, which is fiercely guarded by the Warband's menservants. The marines of the warband spend their time aboard the Heart of Darkness boasting about their hunts, telling tales, trading equipment and swapping possible targets for new hunts. Then, once the get together ends (it has been known to go on for multiple years), the warband splits apart once more as they go marines go their way, searching for a new prey.