This chapter is dedicated to The Red Prince's personal quest.
Stage 1: Fort Joy
The quest starts right after you recruit The Red Prince to your party.
The first character that you must visit is Stingtail. He tells you about Bahara, a Lizard that can be found in Sanctuary Of Amadia. Bahara tells you to find Brahamos who should be in Driftwood.
Stage 2: Reaper's Coast
The quest can be continued after you reach Reaper's Coast. Visit Stonegarden after you unlock Spirit Vision ability and use it near the dragon heads that breathe fire. There, you can meet a spirit of a Lizard. Let The Red Prince talk with him. He reveals important details about The Red Prince's fate.
Your next destination is Red Princess' camp. Let The Red Prince go with Sadha to a cart. This allows you to continue the quest. However, this also means that you will be attacked.
Stage 3: The Nameless Isle
Shadow Prince is located in Lava Fields. Let The Red Prince speak with him.
Warning: Shadow Prince dies if Sebille is also in your party. The Red Prince must talk with him first.
During this conversation you learn that Shadow Prince is behind the attacks on The Red Prince. He explains that he is trying to prevent a birth of a dragon. He thinks that this can have a negative impact on how their race can be perceived by others. He also asks The Red Prince to kill Sadha.
Stage 4: Arx
After reaching Arx you must go to The Consulate where you can find a portal that leads to Sadha (the way of reaching her can be found in the description of The Consulate quest).
There, you can fulfill Shadow Prince's request and kill her.
You can also decide to free her if you have Swornbreaker. After that you can decide whether Sadha and The Red Prince should bring the dragon to life.