You have to seize the throne occupied by Arete in order to complete this mission. The terrain is filled with impassable thick woods but you can burn a large portion of them by activating the dragon veins nearby. There are also four chests located in the middle of the map, separated by thick woods. This terrain can be overcome by fliers so use that to your advantage; just be careful of the enemy archers. There are no kinshi knights here so you can easily gain air superiority against the enemy falcon knights.
Chest contents:
NW: Beastrune
SW: Silver Dagger
Middle: Recover
NE: Excalibur
When activating the dragon veins, make sure it’s during the start of your turn and not in the middle or near the end of the turn to avoid giving the enemies the attack advantage. Regroup and heal and always keep an eye on your enemy’s attack range before placing your units. You can cut through in the middle of the woods to avoid the enemies in the outer path but beware of Arete’s silence spell. She also has a Great Festal that restores HP to all allies in range.
Keep thinning out the enemies. The burned woods due to the activation of dragon veins will restrict much of your ground units’ movements (except shapeshifters like Kaden and Keaton) so be careful not to stray too far or scatter your forces too much. After looting the chests, defeat nearby enemies then take out the queen so you can seize the throne and complete the mission.
After the battle back in your castle, Flora will join your party.