Not only do the many sub-quests in Tales of Arise serve as a nice change of pace from the game's main story, but they're also a great way of earning Gald and SP, which can be used to purchase new armor for Alphen and the rest of the party and unlock new skills respectively. There are 70 of these sub-quests in total, 12 of which can be found in the game's second realm, Cyslodia.