An adult Night Demon Bat's individual ability typically reached Level-17 to 19. A Night Demon Bat King could likely reach Legendary level. What was more important was that these magical beasts lived in groups. Even smaller groups consisted of about 30 of them. Thinking about it, 10 level-18 Archmages could rival an ordinary Legendary powerhouse, so what would it look like to fight with 30 of them? Even a Legendary magical beast would avoid confronting a group of about 30 adult Night Demon Bats.
Night Demon Bat's favorite food was Vampires, so wherever there were Night Demon Bats, Vampires certainly wouldn't get close. Even a Legendary-realm Vampire wouldn't dare to provoke those Night Demon Bats in groups. However, if a Vampire was lucky enough to obtain the fresh blood of Night Demon Bats, then it would be extremely beneficial for its personal growth in abilities.