the knight's plot line is mirroring pizzapants. it is being contacted by and ideologically catfished by somebody that it believes to be december, and is enacting its plan. in chapter 4 it literally thought it was going to meet december in the flesh, which is why it was just hanging around the church, looking around and not really doing anything.

chapter 5 is where both pizza pants and the knight will realize they've been lied to and completely crash out, the latter specifically targeting asgore.