Oryx [i]Took[/i] himself. That's it. That's all it is. If you watch carefully in the mission when he [i]Took[/i] Baxx (the Ogre from the mission when you get a piece of the crystal that Crota's soul was in) and other missions where you get to watch him [i]Take[/i] you will see that it occurs in the same way as what happened in that final cut-scene. If he didn't [i]Take[/i] himself, then he probably just killed himself so he would go to his [b]Ascendant Realm[/b] (Throne World as most people know it) Also, when Eris is speaking to/with her "[b]Queen[/b]", it is likely that Oryx acutally had a wife and she hated the fact that he was becoming so evil, so... when Eris' fireteam killed Crota and then got wiped out, the Queen saved one: Eris. But it's also possible that Eris means Mara Sov but I highly doubt that, although she is the only "[b]Queen[/b]" officially stated to exist in-game.