Orthos, Little Blue, and the arm all share part of Lindon, they are bound to him and share some of their essence. Orthos and Little blue share souls and the arm is physically a part of Lindon.

I disagree that Crusher has a closer bond, Crusher is a parasite that feeds off of Yan Shumei but she has dominated it and forced it to feed off of others. It has made its biggest advancement while in Ghostwater and fed blood from there. Ironically, Lindon might have done Yan Shoumei a big favor in stealing Crushers power and it could give her the tools to rework her bloodshadow.

Is Lindon going to use one of them? No, it would just not be Lindon-like to follow Yerin's path. It could be an option but not likely.