|Heidi Einhard Stratos Ingvalt|
Age 12 (Year 0079)
|Age (as of 0081)||14|
|Age (by depiction)||12-13 (ViVid)
13-14 (ViVid Strike!)
|Magic Type||Ancient Belka|
|Family||Klaus Ingvalt (Ancestor)|
|First Appearance||Magical Girl Lyrical Nanoha ViVid (manga), memory 3: Strike Arts (2009)|
|Voiced by||Noto Mamiko|
Einhard Stratos, full name Heidi Einhard Stratos Ingvalt (ハイディ・アインハルト・ストラトス・イングヴァルト), is the memory successor of the Ancient Belkan Hegemon Klaus Ingvalt. She is a student of St. Hilde Magic Academy, and a DSAA under-15 class world champion martial artist who fights with her self-developed Hegemon Style. Asteion is her intelligent device.
Einhard was born with a rare medical phenomenon known as inheretid memories, meaning she has vivid memories of an ancestor's life, as if she had lived parts of his life herself. Because of this she found herself overcome by her ancestor's feelings of regret over not being able to save those he loved and she developed a need to grow stronger. At the age of twelve, Einhard was already a formidable fighter in her ancetor's style of Strike Arts, which she dubbed the Hegemon Style. Eventually her wish to grow stronger led her to challenge people to street fights around the Midchildan capital city.
Due to her heritage to Belkan royalty, she wished to seek out other descendants to test their strength. As such, she began searching for Queen Ixveria and St. Kaiser Takamachi Vivio which led her to the martial arts teacher Nove Nakajima. After barely winning a fight with Nove, she was taken in by Teana Lanster and Subaru Nakajima for questioning on her actions. Nove was sympathetic to Einhard and wished for her to find a safer way to grow stronger, so she offered to take Einhard under her wing and set her up for a sparring match with Vivio.
Upon meeting Vivio, Einhard instantly realized she was the descendant of St. Kaiser Olivie Sägebrecht, her ancestor's childhood friend and love. Vivio and Einhard quickly became friends and she began both studying martial arts and finding a path to her own dream outside of simply following her inherited memories. In preparation to enter her first martial arts tournament, the DSAA Intermiddle Champtionship, she received an intelligent device from Yagami Hayate and her family. The device, Asteion, was made with Einhard's ancestor in mind as it resembled a small snow leopard, her ancestor favourite animal.
During the Intermiddle, Einhard showed great promise at first. She was able to overcome Corona Timil's Meister Arts and soon found herself face-to-face with another descendant of Belka, Sieglinde Jeremiah. Einhard lost the match against Sieglinde, leading to her first major defeat. During a trip to the Infinity Library, Einhard and her friends were suddenly attacked by Fabia Croezelg, a centuries old witch who knew Einhard's ancestor and viewed him as an older brother.
Einhard's morale was still low after losing to Sieglinde, which Vivio took note of and wished to change. Eventually, Vivio challenged Einhard to a rematch without the safety precautions normally in place for their mock battles and official matches. Showing up in her black St. Kaiser barrier jacket, Vivio fought against Einhard beyond her limits in a reckless way making Einhard feel like she had failed as a senior to the younger fighters. Though Einhard lost the fight, she remembered just how clearly her ancestor loved Olivie and how she feels the same towards Vivio, strengthening her resolve to continue growing stronger. After taking on new opponents with her newfound resolve, Einhard won the DSAA under-15 champion titlebelt.
In summer of 0080, during her morning jog, she happened to run into an exhausted Fuuka Reventon. Just before fainting, Fuuka threw a punch towards Einhard in pure reflex. She couldn't help but recognize the strength of the punch, despite catching it, as well as how quick her reflexes was. Wanting her Hegemon Style of Strike Arts to develop beyond herself, she offers to train Fuuka in her style. Six months later, her effort pays off as Fuuka faces Einhard in the final match of the DSAA Winter Cup. After this, Einhard graduates from her age group and the DSAA under-15 champion titlebelt is soon claimed by Rinne Berlinetta. 
Magical Girl Lyrical Nanoha ViVid (TV anime, 2015)
ViVid Strike! (TV anime, 2016)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 5: Einhard Stratos (2009)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 3: Strike Arts (2009)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 4: Hegemon (2009)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 6: True Feelings (2009)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 60: The Power to Break Through (2014)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 19: Asteion (2010)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 30: Hegemon's Fist, Creator's Wish (2011)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 40: The 4th Round's Prime Match (2012)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 44: Essence (2012)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 47: Infinity Library (2013)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 51: Witch's Memories (2013)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 58: Fourth Match (2014)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 61: Color of the Sky and the World (2014)
- Magical Girl Lyrical Nanoha ViVid (manga), memory 100: Hegemon-style: Einhard Stratos (2017)
- ViVid Strike! (TV anime, 2016), episode 1: Fuuka Reventon
- ViVid Strike! (TV anime, 2016), episode 12: Within the Peace
- ViVid Strike! (TV anime, 2016), episode 13 (OVA): '