"Traps are good, traps we can do," Merlin agreed, although he would hesitate before inviting Ares on any missions. Definitely a last resort. He did not need to be setting up extra screening around his home either, although he would be. The last thing he needed was for more books to go missing because his housekeeper let his double in.
"I detest demons. Did Freyja fill you in on what she had to deal with?" he asked, going to the book wheel and turning to another old text which held the image of a Devil's Trap on it. He tapped it. "Key of Solomon. They used this in that Supernatural TV show to trap their fictional demons, I have a feeling it would be especially potent for this work."