Emeros had already suspected something in the room when he saw the mage's corpse. It wasn't a natural death. It was a Dark Dependent's spell! And a very advanced one at that. It was a spell that called forth the soul.
How a mere mage like Rorcrast would have the power of shamanic and Dark Dependent means similar to the Skeletons and Liches who abandon the flesh, Emeros could only guess that it is connected to the Crown.
But when Emeros saw the corpse and confirmed that it was a Dark Dependent spell that caused the Corpse and not that it died of anything, he read the journal, and there felt dread.
Why did his journal detail his poisoned death? And it was very specific? It was as if he wanted the readers to believe he had died!
At first, Emeros thought that it was to fake his death. But the room itself was strangely habitable. Magic lights worked, and potions and other precious magical stones and ores that were rare in this mine were found inside!