Information about how to recruit Catherine in Fire Emblem Three Hopes.
In Fire Emblem Three Houses you could recruit many characters simply by getting specific stats and skills high enough. Once done, they’d be impressed enough to realize that studying under you would suit them better than petty considerations such as life-long friendships, national loyalty, familial duty or even religious conviction.
Unfortunately characters in Fire Emblem Three Hopes aren’t quite as malleable - some characters will join your faction as you progress the Main Questline, usually due to story contrivances entirely outside of your control. The rest, however, must be met in battle and “persuaded” to join you… often by lumping them on the head enough times to realize that they’d be better off defecting than decomposing.
Character Recruitment Strategies
In the case where a character can be persuaded to join you, this “persuasion” effort is achieved via the deployment of a Strategy. When you start a battle in which a character can be recruited you’ll first have to pick from a variety of available [Strategies]. You can find more information about Strategies on their own page, but for the purposes of recruiting characters you’ll be interested in any “Persuade [Character]” Strategies, which you must select prior to the battle to ensure you can utilize said Strategy(ies) during the battle. Deploying Strategies in turn require you to expend Strategy Resources, a currency gained by completing [Side Quests] during the chapter leading up to the Main Quest where enemy characters can be recruited.
During battle, when the character you wish to recruit spawns you must activate the Strategy to persuade them by entering the battle menu before you defeat them. If you defeat them without activating the Strategy - even if you selected it before the battle - they will die and you will not be able to recruit that character for the rest of the playthrough! Once the Strategy has been activated, the area where the Strategy is in effect (usually where the target character spawned) will be surrounded by a purple glow. Merely defeat them in this area and you’ll recruit the character.
How to Recruit Catherine in the Scarlet Blaze Route
How to Recruit Catherine in the Azure Gleam Route
Catherine can be found loitering around the Base Camp after Chapter 4, but she won’t actually become playable until Chapter 9’s Main Quest battle [Saving of the Silver Maiden]. You don’t need to activate any Strategies to lure her into your service, either - she’s the objective for most of the battle, and once you rescue her, she’ll be playable for the rest of the game. Including for the rest of the battle, oddly enough.
You’ll have to clear the Main Missions during the battle, which mostly involves capturing Strongholds and pulling levers until you open up the northern half of the map. The main threat to Catherine is ostensibly Gwendal, but an allied NPC, Miklan, will keep him occupied for quite a while, and even after the fight between Miklan and Gwendal ends, Catherine can hold her own in a battle with Gwendal for quite a while. Simply put, you’d have to be awfully slow (read: underleveled) for Catherine to actually be at risk. Once you reach her Stronghold along the northern edge of the map and defeat Gwendal, she’ll join you, becoming a playable character for the rest of the battle, and indeed, the rest of the game.
How to Recruit Catherine in the Golden Wildfire Route