An old warlock Osiris, as said in a cut scene before a mission, "...crawl out of the schisms, to swallow light and life." His domain is the trials of "Osiris" And if you travel through the trials undefeated, you shall be reminded of his presence on the lighthouse on mercury. You will also be reminded of your demise as you may not expierence the feeling of being to mercury again in the lighthouse. The war stays strong "trails if Osiris" but he is no longer a combatant because of a life centuries ago.