Aura stealth

 He looked around as he surveyed the forest, but it was peaceful, and he saw no traces of any animals. Aside from the distant sound of birdsong, there was no sign of life here at all.
 At the same time, he observed Lukrut the ranger advancing carefully, keeping a lookout with all his five senses. He seemed to have concluded that there was no living creature hiding nearby.
Actually, there’s someone hiding behind us.
Ainz was proud of the person sneaking behind him.

[...]

Narberal jerked her head over toward the source of the sudden voice. She even thrust her right hand out, preparing to aim and cast a spell. However, her face changed immediately upon seeing who the speaker was.
“Aura-sama! Please don’t scare me like that.”
“Sorry~”
A dark elf girl popped out from behind a nearby tree, with a beaming smile that seemed to say ehehe on her face. She was one of the twin Guardians of the Sixth Floor of the Great Underground Tomb of Nazarick, Aura Bella Fiora.
“May I ask when you arrived?”
“Hmm? I’ve been following behind you and Ainz-sama ever since you entered
the forest.”
Aura was a beast tamer-cum-ranger, so tracking people in the forest was child’s play to her. While it was true that Lukrut was also a ranger, the difference in their abilities was so great that there was no way he could have spotted her.

[...]

 However, there was no need for that. Because her objective was to remove any signs of her passing, she snuck up on her target. Not even her magical beasts, let alone the natural animals of the forest, could detect Aura as she was now.
 Aura proudly walked up to the Wise King of the Forest, all traces of her presence thoroughly erased, and breathed lightly. Her breath contained elements which induced terror, startling awake the sleeping Wise King of the Forest.

- Volume 2; Chapter 3