Oryx isn't being resurrected by any deep exploration. He died in his own throne world - that is a final death for a Hive, laid down by the sword logic and the worm gods. He even acknowledges this himself. [quote]I have died many times but these deaths were only temporary. If my echoes are killed, and I am killed in the material world, then I will be driven back to my throne the Dreadnaught. If my Court and my throne can be beaten, if I am confronted in my throne, if I am defeated there, then I will die. My work will end.[/quote] His death is final. He has failed to prove that he is the most ruthless or powerful, his existence has become a lie. Savathun and Xivu were only resurrected because their deaths were temporary, Oryx trapped them deep in their own throne worlds. Oryx even contemplates killing them permanently and subsuming their thrones into his. When they say true death, it means that they were killed by the sword logic and Oryx took their power for himself. He took the speed and might from Xivu and he took the power of cunning from Savathun.