There are several secret characters in Fire Emblem Warriors: Three Hopes that can be unlocked when you meet certain conditions. Take a look at our How to Unlock Secret Characters guide to find out what they are.
Arval is Sothis' counterpart in Fire Emblem Warriors: Three Hopes and in order to unlock her as a playable character you will first need to complete the main story on any difficulty setting and also successfully recruited Byleth. Take a look at our How to Unlock Byleth guide to find out how this is done. If you fail to recruit Byleth but still complete the game you will not be able to recruit Arval on that playthrough.
Once you have completed the game meeting these conditions and the credits have rolled, you can load up your final save file and purchase Arval from 'Your Quarters' in the Camp for 60 Renown by interacting with the journal on the desk and selecting the option that says 'Spend Renown'. Keep in mind that Renown is limited by chapter, so you need to make sure you have saved up enough in advance. Arval isn't retroactively available in previous save files so you need to either purchase her in your end-game save file or in a New Game Plus file created based on the end-game save where you unlocked Arval.
Rhea and Sothis can be unlocked as playable characters in Fire Emblem Warriors: Three Hopes the same way as you unlocked Arval except you do not have to unlock Byleth. It does not matter which ending you get. Similar to Arval you will be able to purchase Rhea and Sothis for 60 Renown each once the credits have rolled by loading up your final save file and interacting with the journal in 'Your Quarters' in the Camp.
Take a look at our Beginner Tips and Tricks to get help in Fire Emblem Warriors: Three Hopes.
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