From The Grey House, Book One:
It took a long time to convince the Slayers that The Red Thread was a better target. Zechariah, for some reason, was convinced The Ocean’s Edge needed to be destroyed. Natalia thought perhaps Zechariah wanted to make the headlines instead of killing Hellspawn. She was finally able to convince Zechariah a few months ago to use The Red Thread, and now Zechariah knew what to do there. Natalia didn’t know what he was planning. She could guess though, and the guesses weren’t very pleasant.