Chapter 229: Change

The letter wasn't supposed to be found at this time. Moreover, it wasn't supposed to be found out by her. 

When Castiel created his Generals, he had also selected one person amongst his Generals for an even more important mission. 

He had selected his first General to come to the place where he was going to be sleeping. Castiel had also told him about the location and everything. 

His General was supposed to get there, and he was supposed to be the person who took over the body for a brief period. Since it was the first Vampire that Castiel created, he wasn't going to have much burden on his soul, and he could also return to his real body after his work was done. 

That's also why Castiel selected a person who was in his early twenties to become his First General with this mission that was supposed to take place after a few decades.