Castiel hadn't been asking how Skulduggery had died, but how he'd still lived, and the answer he received was largely uninformative, to say the least. Both of them would rather learn more about the other than explain themselves, and Castiel eventually caved, realizing that he might not get Skulduggery to explain further unless he revealed something more about himself.

It was no surprise that someone who'd died wasn't that shocked by the existence of divine beings, but Castiel doubted that Skulduggery would recognize his name. "I'm Castiel," he said. "My name doesn't appear in the Book, so there's no reason that you would know of me." Not to mention that that Book was rather inaccurate, colored by the perceptions of humans who understood so little.

They were getting closer and closer to the town, which meant that Castiel had only so much more time to find out what he was curious to know. For that reason, he didn't hold back with his questions. "So you were murdered and then... cursed? To an eternal life in death?" It was only a guess, but it seemed the most likely, which meant that someone powerful had held a large grudge against Skulduggery for some reason.