Okay, I think I understand the confusion, but I hope I can clear it up for you.

As stated in the sidebar on Chapter 2: wyrmspeakers are all Wearers of Purple. That's the upper-most group in the cult. That same line says that wyrmspeakers can appoint other cultist to preside over cult enclaves, making those appointees also Wearers of Purple.

Going back to the Preface, it says there are no formals grades within the ranks of Wearers of Purple. Presumably that means that to your everyday cultist from initiate up, whether a Wearer of Purple was a dragonclaw (lowest-rank cultist) or a dragonsoul (just under wyrmspeakers), you have to treat them like they were a wyrmspeaker. In other words, Wearers of Purple are essentially the hands and voice of the wyrmspeaker themselves when the wyrmspeakers cannot be physically present.

The Prisoners mission simply says that that mission provides an excellent time to introduce players to the Wearers of Purple through a glimpse of Frulam Mondath, but you could have introduced her on one of the other missions.

Okay, I think I understand the confusion, but I hope I can clear it up for you.

As stated in the sidebar on Chapter 2: wyrmspeakers are all Wearers of Purple. That's the upper-most group in the cult. That same line says that wyrmspeakers can appoint other cultist to preside over cult enclaves, making those appointees also Wearers of Purple.

Going back to the Preface, it says there are no formals grades within the ranks of Wearers of Purple. Presumably that means that to your everyday cultist from initiate up, whether a Wearer of Purple was a dragonclaw (lowest-rank cultist) or a dragonsoul (just under wyrmspeakers), you have to treat them like they were a wyrmspeaker. In other words, Wearers of Purple are essentially the hands and voice of the wyrmspeaker themselves when the wyrmspeakers cannot be physically present.

The Prisoners mission simply says that that mission provides an excellent time to introduce players to the Wearers of Purple through a glimpse of Frulam Mondath, but you could have introduced her on one of the other missions.

Edit: There is also Langdedrosa Cyanwrath somewhere about town. While never explicitly named as a Wearer of Purple, he has enough pull within the cult to release prisoners, his own personal troop of followers, is rumored to be Mondath's right-hand man, and is pictured in purple on page 17. So a DM could have Cyanwrath be the example Wearer of Purple the party first spots. Regardless none should actually be encountered until the end of the chapter, where the party will meet Cyanwrath.

Okay, I think I understand the confusion, but I hope I can clear it up for you.

As stated in the sidebar on Chapter 2: wyrmspeakers are all Wearers of Purple. That's the upper-most group in the cult. That same line says that wyrmspeakers can appoint other cultist to precise over cult enclaves, making those appointees also Wearers of Purple.

Going back to the Preface, it says there are no formals grades within the ranks of Wearers of Purple. Presumably that means that to your everyday cultist from initiate up, whether the a Wearer of Purple was a dragonclaw (lowest-rank cultist) or a dragonsoul (just under wyrmspeakers), you have to treat them like they were a wyrmspeaker. In other words, Wearers of Purple are essentially the hands and voice of the wyrmspeaker themselves when the wyrmspeakers cannot be physically present.

The Prisoners missions simply says that that mission provides an excellent time to introduce players to the Wearers of Purple through a glimpse of Frulam Mondath, but you could have introduced her on one of the other missions.

Okay, I think I understand the confusion, but I hope I can clear it up for you.

As stated in the sidebar on Chapter 2: wyrmspeakers are all Wearers of Purple. That's the upper-most group in the cult. That same line says that wyrmspeakers can appoint other cultist to preside over cult enclaves, making those appointees also Wearers of Purple.

Going back to the Preface, it says there are no formals grades within the ranks of Wearers of Purple. Presumably that means that to your everyday cultist from initiate up, whether a Wearer of Purple was a dragonclaw (lowest-rank cultist) or a dragonsoul (just under wyrmspeakers), you have to treat them like they were a wyrmspeaker. In other words, Wearers of Purple are essentially the hands and voice of the wyrmspeaker themselves when the wyrmspeakers cannot be physically present.

The Prisoners mission simply says that that mission provides an excellent time to introduce players to the Wearers of Purple through a glimpse of Frulam Mondath, but you could have introduced her on one of the other missions.