Embrace the Dark (闇へと進みゆく Yami e to susumiyuku, The Descent to Darkness in the Japanese version) is Chapter 6 of Fire Emblem Fates in the Conquest Version. Rinkah and Sakura permanently leave the party at the beginning of this chapter, while Kaze leaves until the end of Chapter 11. Xander, Camilla, Leo, and Elise temporarily join in this chapter, but they gain no exp. Felicia/Jakob rejoins in this chapter. Azura temporarily leaves the party after the chapter is over, and returns in Chapter 9.
The script for this chapter can be found here.
Subjective: The following part of this article is based upon the editor's personal experiences and opinions, and therefore may not be applicable for all readers.
The objective is to defeat four enemies, even though there are 5 on the map. Jakob/Felicia (each one depending on the Avatar's gender) will rejoin at the start of the battle. There is a slight change depending on difficulty, but it is typically negligible.
The five enemies on the map are simply Ryoma, Hinoka, Takumi, Sakura and Yukimura. Ryoma is the hardest of the five, due his high speed ensuring most attacks will miss him. Xander is closest to Ryoma. You can either fight him, or move Xander away.
Hinoka and Takumi are in Guard Stance, though they are still relatively easy to defeat. While you fight those two, you can have Xander move for Yukimura and Sakura, as Ryoma is typically not worth fighting regardless of the difficulty you play in.
Ensure that only your Avatar and Jakob/Felicia finish off the enemies, as the Nohrian siblings will not get any experience upon defeating the enemy.
Should Camilla, Leo, Xander, or Elise be defeated in this chapter, they are not permanently defeated, and can still be recruited in later chapters. However, if either the avatar or Jakob/Felicia fall, then it's a game over for the former and permanent removal from the game for the latter.