The script for this chapter can be found here.
Subjective: The following part of this article is subjective to the editor's writing. Therefore, it may not work for everyone.
The goal of the map is to Seize the fortress that Arete is standing on, which can vary in difficulty depending on if you choose to go for the treasure chests in the woods or not.
The enemy units include Swordmasters, Snipers, Spear Masters, Oni Chieftans, Falcon Knights Master Ninjas, Mechanists, and Onmyojis. Arete, the boss, is a Strategist, and there are two Faceless very similar to the faceless Anthony from the previous chapter, in that they posses the Immobilize skill. Basara and Kinshi Knights will also appear as reinforcements.
The gimmick of the map, if you choose to indulge it, are the various Dragon Veins dotted around the area that erase large chunks of the Thick Wood that occupy most of the map, replacing them with Woods tiles. Though you can use all the Dragon Veins to erase all the Thick Woods and convert them all into normal Woods, you can alternatively have a flying unit who either has lockpick, has numerous Chest Keys, or is carrying a lockpick unit go to the chests directly without initiating too much battle, though the enemy Falcon Knights can go through the Thick Woods as well without issue.
Otherwise, you simply need to get to Arete, defeat her, and seize the fortress. This is easier said than done, as both paths around the Thick Woods are being guarded by numerous enemy units. The bottom path is especially dangerous to Wyvern units and Corrin because of the Onmyoji who drops Dragon Spirit, which triples in weapon might when attacking them. Arete's also has Great Festival to restore the HP of all units in range, and she will recover a good bit of it, though she is limited to using the staff twice. She can also silence any magic or staff users, so you might want to wait on attacking her until she loses the staff.
Being a magic user, Arete can deal serious damage to many of your units who have low Resistance growths, so be careful when using them. Since she is also positioned in a fortress, you will deal less damage to her and can't hit her as often as usual. This is about as far as the difficulty extends, as her defensive ability is rather low, and she is very easily doubled by any unit with more than 23 speed and is not using a weapon that lowers effective speed. Her stats do improve on higher difficulties, but the best counter if problems arise is Kaze, so long as he has retained use of Shuriken and Knives that hold weapon advantage over Arete's scroll. Even if he can't kill her in one round, he should easily remove a large chunk of her HP and take minimum damage in return, on top of lowering her stats depending on the weapon used, and let another unit finish her off. Felicia can also technically serve the same role, but her strength at this point in the game, as well as Arete's fair amount of Resistance, mean she doesn't leave as big a mark.
Reinforcements begin to appear on turn 9, starting with a Master Ninja from the unoccupied fort south of the upper-right chest.
Turn 11: Two Basara from the pathway behind the player armies starting point.
Turn 13: A Master Ninja from the fort just below the bottom-right chest containing Recover.
Turn 15: A Master Ninja from the leftmost fortress on the map.
Turn 19: Repeat of Turn 11.
Turn 25: Three Kinshi Knights from all three forts.