Treason

"Nohr now controls the Hoshidan capital, but the real battle is just beginning. The children of Nohr stand together to face a treacherous enemy."

- Opening narration

Treason (悪逆 lit. Treachery in the Japanese version) is Chapter 26 of Fire Emblem Fates in the Conquest Version.

Script
The script for this chapter can be found here.

Strategy
Your units start off at the top of the map, while the area to seize is occupied by Iago in the middle of the room. There are several doors blocking the way to him, so a Locktouch unit will be needed to open them. Alternatively, your units can simply break down the doors using weapons. The room entered will contain Heroes, which should not be much of a threat as they can be picked off easily. Once that room is cleared, there are two doors, one on either side that can be opened. The left side will contain Faceless and Golems, while the other side will have Sorcerers and Maids. If your units are physically defensive, they should take the left side while magically defensive units should take the right side. Both sides also have one chest, and can be looted before leaving. The bottom room contains both Generals and Berserkers (including Hans), who will rush over to the closest side players are entering from. Since Hans is extremely dangerous on Lunatic, the player may opt to use an Entrap stave on him so that they do not need to worry about him when they reach the bottom.

Iago should be dealt with carefully, as he carries Enfeeble, Silence and Freeze staves. His Infinite Staff skill will boost their range to 10 and provide unlimited charges. On Lunatic, this is worsened as he is given a Hexing Rod which can cause easy resets if he manages to get lucky with them. Fortunately, on all modes, Iago follows a staff rotation and will never use the same staff twice in a row.

Once they are cleared, open the door leading to Iago. Once you defeat him, remember to loot the three chests near him before seizing the stairway.

Dropped Items

 * Excalibur - Iago
 * Aurgelmir - Hans

Chest Items

 * Spy's Shuriken (left most chest with the Stoneborn and Faceless)
 * 20,000G
 * Seraph Robe
 * Venge Naginata
 * Bifrost

Enemy Reinforcements
When an ally unit enters the attacking range of the Sorcerer at the bottom, there will be reinforcements at:

A1

When an allied unit enters the attacking range of the Faceless at the bottom, there will be two Faceless reinforcements in the staircases to the left (Hard mode)

When Hans or one of the two Generals in front of him get aggro'd, there will be two Berserkers and Generals spawning at the four staircases at the very bottom.

Avatar vs. Iago

 * Iago: Are you ready to pay for your betrayal, Lord Avatar?
 * Avatar: No, Iago, I am ready to kill you.
 * Iago: Oh my, how very frightening. I'm trembling! I am the highest-ranking general in the Nohrian army, you fool. Do you really think I'll be so easy to kill? But before you die, I have something to tell you. A parting gift, if you will. It was I who sent the Faceless who killed that flying rat, Lilith.
 * Avatar: What!?
 * Iago: Oh, and that's not all. It was I who suggested to King Garon that you be forced to kill Prince Ryoma. And I who told the enemy about your journey to Macarath. Did you enjoy my little gifts of sorrow? I put ever so much thought into them!
 * Avatar: I will never forgive you for all that, Iago. Prepare to die!
 * Iago: Ha! So the imprisoned little prince fancies himself all grown up. The king ordered me to make you suffer without killing you... But I can no longer comply. In order to see my plans to fruition, you must die! Say your prayers, Lord Avatar!

Other vs. Iago

 * Iago: You impertinent traitor! Your ragtag group is no match for my army! Let your death serve as an example to all those who dare oppose King Garon!

vs. Hans

 * Hans: I've waited a long time to wipe that smug look off your face. This is what you get for not bowing down to my might!

Trivia

 * Iago does not consume charges on the wands he has in his inventory, so he can and will consistently use all three of them during the course of this chapter without their charge count going below 4.
 * Though he does not consume usage of these staves, he is confined to a staff rotation on all difficulties and will not use one staff twice in a row.