This is a grind location to easily save 20 rebels. This requires the skill "Dawn & Dusk", which makes this entire process quicker. Head to the Walls of the Ruler citadel. Even if you have completed the location, it will repopulate with enemies and captured rebels. Go in and save the rebels, if you remain out of combat when doing so, use the Dawn & Dusk skill in the citadel to fast forward time, causing the captured rebels to repopulate. You may need to use the skill multiple times before repopulation occurs.
Here is a video guide with English commentary!
Here is a playlist of guides for this game!
https://www.youtube.com/playlist?list=PL-HeW6XkKdULDFgDhklKO...