Spiritual Leader is an external NPC that leads Spiritual Guidance sessions in a Chapel. One also comes in for execution. Due to the chapel being multi-faith, the kind of NPC spawned is random. It is also noted that you will need a work schedule for this in order for the spiritual leader to show up.
Just like the Teacher or National Guard, he will come once you build the required requirements for him to show up. you will need to build a Chapel and need to start the Spiritual Guidance program for him to show up.