Chapter 18A: Leo

The map is small and will be riddled with life-draining marshes. The dragon veins in the map are only accessible to Leo which can be used to create more marshes that will hurt only non-Nohrians. The avatar, Kana (avatar's son/daughter), Silas, Jakob, Dwyer (Jakob's son), and Felicia will be immune to the marsh's effects so bringing them in this battle can give you a bit of an edge. Leo is also accompanied by two characters (recruitable only on Conquest) Odin and Niles, which can drop a Horse Spirit and Silver Yumi respectively. Don't assume there's only three of them; as soon as the battle starts, several Faceless enemies will appear from the marshes and surround your team.

Have your Hoshidan allies avoid the marshes if they can and stick with the Woods terrain to get some advantage. Leo can be reached and defeated easily especially if you'll utilize your fliers but it's worth defeating Niles and Odin first to loot the good weapons they're carrying before finishing Leo off.

Take note that the Faceless will just keep appearing as well so you'll have to defeat Leo as soon as you looted Odin and Niles to avoid getting overrun. Otherwise, if you're confident about your team's strength, you can hang around a bit until the Faceless reinforcements run out to farm easy EXP and at the same time, increase your characters’ weapon proficiencies.