Inside Oblivion, upon seeing that Primordial Soul was gone, Rowan did not panic; he had never expected that he would be able to find the body of Primordial Soul before now, and learning she was no longer imprisoned was a good thing for him because one of his greatest hidden dangers had been broken.
This was indeed a remarkable gift from Eosah, even though Rowan was a bit disappointed about not getting Primordial Soul on a platter. No Primordial worth their salt would endure an eternal prison.
The two things Rowan needed to be worrying about now were when and where. When did Primordial Soul escape, and where was she?
The when was easy enough to figure out if his hypothesis was correct: Primordial Soul used the act of Primordial Time peering into the future to awaken Eos, who was Rowan.
Maybe because he was born before his time, or maybe because his mother Eosah was already dead, or Rowan was not even given the time to awaken to his nature, Primordial Soul had killed him.