The Legend of Heroes: Trails of Cold Steel

Arts is a form of magic that usually takes a couple of turns to cast. You can tell when an enemy is about to use it when a magic circle appears around their body. You will then need to use your main character's craft: Autumn Leaf Cutter or other character's first craft (such as Alisa, Fie, Jusis, and Machias as long as their craft has Impede ability) as well before the enemy has a chance to cast the magic. This skill will delay the enemies' turn, and will also prevent them from casting their arts. Same thing applied to enemy's craft since it still takes time to cast it.

You can also equip the quartz Impede 1 (30% chance), Impede 2 (60% chance), or Zeus Gem (90% chance) on some characters, so their normal attack or craft can cancel the enemy arts.

Note: Impede 1 and 2 can be exchanged at George's Shop or other Orbal Shop. While Zeus Gem is a rare quartz which you can receive one from Treasure Chest in Chapter 6 or if you already have Master Quartz Thors, then pick the same choice when the principal asks you to choose one of two Master Quartz.

There is a story-related boss in Chapter 6 where you can grind this trophy as long as you have quartz above mentioned on every character or use their craft which has Impede ability. After you defeat the Monster (Hydra) from the quest Nortia Highway Monster, save the game then remove all STR-related accessories and quartz. Also don't use a strong weapon (equip weak weapon if you have some) before going back to Roer for an Event, then you have to fight against the boss: Gespard G.

This boss will use normal attack for a few turns, then it tends to use craft (similar to using an art, but it takes time to cast), so you should let Elliot take a role of healer and use other character's normal attack or first craft to attack the boss whenever it prepares to cast the craft, repeat until you unlock this trophy. Please note that if you miss a chance to cancel the boss' craft, then it will takes a while for the boss to use the craft again.

Note: You can check your progress in Battle Note under Combat Skill - Cancel Arts