White Snake Sage

The is the leader of the snakes of Ryūchi Cave.

Background
At some point, Orochimaru discovered the location of Ryūchi Cave through his study of Jūgo's unique powers, and began studying there to master Senjutsu under the White Snake Sage. Unable to attain Sage Mode, he instead developed an alternate method of harnessing his senjutsu chakra through cursed seals.

Sometime after injecting himself with Orochimaru's remains, Kabuto Yakushi discovered Ryūchi Cave and received the White Snake Sage's teachings. Under her guidance, Kabuto was able to learn senjutsu and ultimately mastered the use of Sage Mode.

Personality
In the anime, Orochimaru referred to the White Snake Sage as a being with an eccentric personality and very dangerous to deal with. She has a strict policy of only letting her subjects eat any intruders if they first fail any of the given tests that would allow them to meet with her. Overall, the sage is shown rather laid-back and uninterested in matters that don't directly involve Ryūchi Cave.

She dislikes Garaga, who causes nothing but trouble for the rest of the snakes due to his violent disposition. She tolerates him for being useful in disposing of humans who annoy her, sending humans on a fools errands to try taking his reverse scale.

Appearance
The Sage is an extremely large, albino Japanese rat snake many times the size of a human, who sits upon a sacred seat with her massive body wrapped in thick coils. Along these coils are yellow circular bands. She wears a turban with two pointed edges and a red orb on top along with an orange headdress. She also wears a chain with a green orb around her neck, similar to the one worn by the Great Toad Sage. Because she has lived in the cave for so long, her body has grown together with the ground. The Sage also smokes, using a long cigarette holder when doing so.

Abilities
As a sage, the White Snake Sage is highly knowledgeable in senjutsu and capable of passing on her teachings to others. She is able to inject others with natural energy using her fangs, which she does to those who seek out her training. According to legend, if the trainee's body is unable to withstand this power and transforms into a snake, she will swallow them whole without reservation. In the anime, much like her subjects who are responsible for the cave's trials, she can use genjutsu to make others experience visions, which she can use to relay the thoughts of other snakes to third parties, as well as disguise her true form, to the point of often taking the form of an elderly lady.

Mitsuki's Disappearance Arc
In the anime, the White Snake Sage granted an audience with Boruto Uzumaki after he passed through the Ryūchi Cave's trials. When asked to analyse the snake he brought in hopes of learning more about Mitsuki's departure, the sage refused, saying the trials Boruto passed were about earning the right to learn senjutsu. Boruto insisted, and the sage agreed to help him if he brought the sage Garaga's reverse scale, though the sage fully expected Boruto not to survive the attempt.

The genin soon after all returned. When the sage asked for the Reverse Scale, Boruto, having entered a contract with Garaga, summoned him. Technically upholding his promise of bringing her the Reverse Scale, the sage revealed the secret thoughts inside Mitsuki's snake. It showed that Mitsuki feigned killing a guard to save his life and joined the attackers to the Land of Earth. As the genin made their way to their next clue, the sage noted that Boruto has a strange destiny before him.