User blog comment:IamJakuhoRaikoben/Chapter 364: Tartarus Arc, Part 1: Sins and Sinners, Review./@comment-5036235-20131220072132/@comment-7418318-20131220102527

Even if KotSS is canon, it'd make sense for Erigor not tag along with the OS, considering how much he regretted the decision to join them and give up his memories after Wendy healed him.