Board Thread:Warhammer 40k General Discussion/@comment-25507520-20150422230011/@comment-25507520-20150518172259

Hey, so after this im pretty sure that all Eldar, even the Dark Eldar, must die in order for Ynnead to be formed.
 * Phoenex - The Phoenex are a hidden offshoot of the Ever-Nemesines. They seek to forge the Eldar race anew by the means of actively exterminating their own kind, be they Commorrite, Craftworlder, Harlequin,Corsair or Exodite. They believe that should the Eldar become extinct, Ynnead, the god of death, will be awakened and the spiritual malaise of the Eldar lifted forever. The Phoenex is the most secret of all brotherhoods, for their eagerness to see their brethren slain could easily see them undone. It is whispered that their morbid philosophy is not limited to Commorragh. Some say that entire troupes of maverick Harlequins -- and even the spiritual leaders of more than one Craftworld -- share the Phoenex's goals. When the Eldar are ready to be reborn, the practitioners of this philosophy intend to be the ones in control, guiding their race's destiny from guttering spark to glorious inferno once more.

This is from the Haemonculous page.