Elfie was still in shock at how her new master just call her name. She hadn't had the chance to introduce herself, but Tom already knew her name.
Magic was strange with all kinds of abilities. Knowing someone's name might not seem much, but the situation this time was different. Elfie was a low Diamond Rank magician, so she had spells protecting her at all times. This included protection from someone to peer through her.
Magician could curse someone just by knowing their true name. Which was why the fact that Tom could find out about her true name was very terrifying.
Tom already knew about the existence of curse magic. He just did not want to learn about it, because it wasn't very effective at killing. At best, it could annoy someone and they needed to buy expensive potions, but that was it.
He wanted abilities that could make his enemies explode with a single attack. Something fatal and deadly, making anyone that witness it trembling in fear.