"So, if you don't speak, it means you agree?" there is impatience in Violet's tone, in fact, she indeed feels this way, for now, she doesn't want to see anyone standing in her way.
Their duty is to guard here, preventing anyone who might want to barge into Black Crow Castle from causing trouble. There's no reason for the captain of the guard squad to step aside for her.
This unavoidably leads to a conflict. The mercenaries in heavy armor raise their shields, informing Violet by their actions that they're prepared to deal with her.
Without bothering to utter another word, Violet skilfully snaps her fingers, and a black card materializes in front of her.
At the sight of the card, the mercenaries, who are seeing it for the first time, feel a sense of curiosity, as they've never seen this way of casting magic before.
However, very soon, their curiosity turns into fear.
The card summoned by Violet is a low-level spell, merely a first-tier Frostbite Skill.