Ingvild is a beautiful young woman with long purple hair and has orange eyes, with her appearing in her late teens and she wears a white noble dress.
After joining Issei’s peerage and becoming a student at Kuoh Academy, Ingvild now wears a female school uniform.
Ingvild is a kind and friendly person and enjoys singing as is shown when she sings at the fountain and for Issei and his group. Ingvild is also shown to love seeing the ocean and going on beaches with her friends. Unlike her fellow members of the Leviathan clan or any other descendants of the original Satans, she doesn’t have an evil heart and doesn’t wish to rule the Underworld. She also appears to be quiet, shy and soft-hearted.
Ingvild was born as a child to both a human and a devil from the Leviathan clan and was living in the human world in the seaside city in Europe. At some point in the past, she ended up with a devil disease that made her enter a deep sleep and so Ingvild was sent to the underworld in an attempt to cure her of the disease. Because of this, she continued to sleep for a hundred years. She was then woken up due to her Longinus Nereid Kyrie beginning to take its form.
Red Dragon Emperor of the Blazing Truth × White Dragon Emperor of the Morning Star: The True Dragon(s) of the Kuoh Academy
Ingvild made her first appearance in True Volume 1, and was singing by the fountain which Issei was killed by Raynare. While biking to his house, Issei hears her singing and follows where it is coming from and as she stops singing, she realizes he’s the red dragon. They soon get attacked by the unidentified devils and, as a result, Ingvild stands behind Issei. After Issei defeated the unidentified devils, Ingvild was covered in blood from her dress to her face and used the handkerchief that Issei gave her to wipe the blood from her face. She looked at her hands covered in blood and calls it beautiful because it’s more of a crimson color and Issei’s armor is the same color as well. Ingvild then vanished without a trace after Issei called in Rias. She appears again after Issei and his friends were fighting the unidentified devils and she starts singing again, which causes Issei and Bova Tannin to partially kneel down in pain while affecting Ddraig as well. To stop her singing, Rossweisse wrapped her in a light blue aura, and used her hypnosis magic to control Ingvild as well as make her temporarily fall asleep.
Ingvild was sleeping in one of the rooms of the Hyoudou Residence and when she wakes up, Ravel sends Issei and Asia to talk to her. Ingvild then asked them to tell her if she is in Issei’s house which Issei confirmed and introduces himself and Asia. Ingvild then introduces herself but remembers her surname which the people in the hospital called her: Leviathan. Issei asked her why she was at the fountain which she answered the Sea and also said that she heard that everyone including her parents had already passed away. After having a brief conversation about how Ingvild wants to see the ocean, Asia suggests that everyone go to the beach. While at the beach, Ingvild is standing on the sand and looking at the ocean when Issei goes to talk to her. Issei tells her that he likes her singing and she thanks him for bringing her to the sea, and they converse where she reveals that she was born in the seaside city and loves the ocean. Issei tells her to go to the sea with him but she said she will be taken somewhere where her powers are going to be studied. Issei, however, tells her he will take her. Ingvild laughs at the fact that she became friends with the Oppai Dragon and Issei tells her to call him by his name since they are friends and invites her to eat with Rias and everyone else, but their conversation was interrupted by Nyx who appears from the sky with the intention of obtaining Ingvild in order to use her to control powerful dragons like Issei, Vali, Crom, Ophis, and Great Red. Nyx tells Ingvild her to sing which caused Issei to suffer pain again and she passes out due to the brainwashing technique caused by Nyx.
After being brought back to the Hyoudou Residence and being allowed to sleep for a while, Ingvild awoke and overheard Cao Cao's assessment that she would have to be sealed which could result in her being unable to awake again or be killed to prevent her power being misused. Realizing that her power could bring trouble to a lot of people, Ingvild stated that she was okay with being killed. This saddened Issei, who implored her to reconsider her choice as he stated that he would be sad if she were to die, which shocked her. After hearing Asia's plea, Ingvild reconsidered her choice and begged Issei to help her, as she did not wish to lose another friend, to which Issei responded by promising to defeat Nyx. She later was present when Issei and the rest of the Occult Research Club departed to defeat Nyx.
Ingvild was contacted by Issei through Akeno’s breast and asked her to sing for him. She became hesitant at first due to the pain she caused when she sang but agreed when Issei begged once again. Her song has been heard throughout the battlefield through by the breasts of the girls and powered up everyone. After Nyx was defeated, the brainwashing spell that was placed on Ingvild was removed by Rossweisse and she thanked everyone for they did for her. Issei’s queen piece began to glow and Ingvild also glowed, causing Issei to believe that he has found a suitable servant and asked if she can sing while being his servant which he agreed. Ingvild became Issei’s first servant and grew out eight wings due to her being the descendant of Leviathan, to which Issei agreed to help her put her wings away. After becoming Issei’s servant, Ingvild appeared at the Occult Research Club where Beelzebub informed the group that the Olympian gods Hypnos and Oneiros had offered to help treat Ingvild of her sleeping disease to which she agreed.
In True Volume 2, Ingvild appeared in Issei’s dream of him marrying his brides, with Ingvild among the first group and she became confused if she became a bride. In the morning, Ingvild went together with Issei, Ravel, Ouryuu, and Bova to do their morning marathon and she became used to running like she used to run back in her hometown, but became harder for her because of her sleeping disease. After finishing the morning training, Ingvild was informed by Issei about her devil job and she was accompanied with him, due to her demonic power being too vast for the teleportation magic circle. Ingvild meets her first consumer Lavinia Reni, who thanks her for coming to help her with unpacking for the person who is moving into Kuoh Town, which turns out to be Vali Lucifer. She meets a another member of SlashDog Natsume Minagawa, who shook hands with and hopes to get along with her. After finishing her devil job, Ingvild received a white dragon plushie as gratitude from Vali and returned to the Hyoudou office with Issei.
In the night, Ingvild and the other girls catches Akeno and Koneko attempts to seduce Issei in Akeno’s erotic room and she wonders about hugging Issei naked, but finds it embarrassing, and she and the others ended up sleeping with Issei. Ingvild joined Issei and his team to their training camp in the mountain for training, she began her training at the small river to master her water magic in a form of a eastern dragon, and trying to master her clan’s specialty Sea Serpent of The End and after putting back the water back into the river, Ingvild started to feel drowsy and took a break from her training. Ingvild and the two teams celebrated Issei and his team victory at the Hyoudou Residence and as Issei recalls the second year students trip, he tells Ingvild to fun at Kyoto, which she happily agrees.
In True Volume 3, Ingvild was half-asleep during the meeting of the Occult Research Club about doing a program they will be doing during the autumn event at Kuoh Academy. The group began talking about Kyoto, with Issei telling Ingvild to enjoy Kyoto and doesn’t need to worry when she is with Ravel and Koneko, which she happily agrees and tells Ravel and Koneko that she is under their care.
Powers & Abilities
Immense Demonic Power: As a Devil who is a descendant of the original Leviathan, Ingvild possesses an impressive amount of demonic power and has all the common skills and powers of one. Ingvild has the ability to teleport as she subconsciously teleported to the park in Kuoh Town. According to Rosswiesse's measures, the amount of aura Ingvild posses is equal to a Satan-class Devil or even higher.
- Sea Serpent of the End (掉尾の海蛇龍 Tōbi no umihebi ryū) : As a descendant of the Leviathan Clan, Ingvild has the ability to control the sea and draw large amounts of water. At full power, she's capable of summoning floods, drown whole cities and create a snake-shaped Dragon made of water.
Magic Expert: Her demonic power is enhanced due to the Bishop trait of her Queen Piece. Rossweisse describes Ingvild as a genius as she's managed to show knowledge with elemental magic.
Enhanced Speed, Strength and Defense: Due to the Knight trait and Rook trait of her Queen Piece, Ingvild has superior speed, strength and defense.
Stealth Expert: Ingvild is shown to disappear without leaving a single trace, as Issei didn’t felt her presence leave.
Flight: Being a half-Devil, Ingvild can fly using her 8 wings.
Nereid Kyrie: A High-tier Longinus with the ability to manipulate Dragons and the Sea.
- Breast Song Reinforcement: By using Issei's Diabolos Dragon God as a conduit, Ingvild can empower Issei and his allies who are present. The song can be heard through the breasts of women as the area is bathed in lavender light particles.
- Ingvild is named after the famous Norwegian actress with the same first name. 
- Ingvild and Asia are the only characters to be named after two celebrities.
- Ingvild is the second descendant of the original Satans to be a devil/human hybrid, with the first being Vali Lucifer.