Kaylin doesn’t get to use what little magic she has often, but her control of it is extremely high because of her subclass as a Spell Thief. In the game, the special effects when casting a spell could be customized to a point (you couldn’t just fully remove them but you could use some tricks to make them harder to see the effects to help catch people off guard). Here Kaylin has started the casting of her darkness spell but is just manipulating the pre-spell effects to create a dancing shadow displaying her control and practicing it.