In Fire Emblem: Thracia 776, it is implied that Nanna and Delmud may have different fathers: Delmud is Beowolf's son, while Nanna is believed to be Finn's daughter, essentially making Delmud and Nanna half-siblings.
Nanna first appears alongside Finn and Leif in Leonster at the start of Chapter 7 as a playable ally. It is revealed through her conversation with Delmud that Raquesis came to Leonster after the Battle of Belhalla and thereafter left Nanna in the care of Finn, disappearing later to search for Delmud. As a result, she grew up together with Leif, lacking any knowledge of her mother's whereabouts.
Nanna, alongside Leif and Finn, join Seliph's army when they come to their aid. She is then reunited with her brother, Delmud, and her cousin, Ares. She will learn that Raquesis is still missing while conversing with Delmud. After capturing Conote, she can share a conversation with Ares, whereby she explains that Sigurd is not Eldigan's murderer.
After the war, if Nanna has been paired up, she will accompany her husband to his homeland. If she is not paired up, she will then return to Nordion with Ares and Delmud.
In this game, Nanna grows up with Leif in Fiana. They arrived in this village at a young age, accompanied by a badly-injured Finn. After hiding in other locations such as Alster and Tahra, Raquesis will finally join them. She will then promptly disappear in her quest to reunite with Delmud and Ares Eyvel will then take on a mother's role, raising Nanna and Leif on Raquesis' behalf. In the later events of the game, Eyvel and her adoptive daughter Mareeta will be kidnapped by Raydrik, but will eventually be rescued by Leif's liberation army.
After the liberation war, Nanna will wed Leif and assist him in the reconstruction of Leonster, as well as the New Kingdom of Thracia. Her kind and selfless nature will eventually earn the admiration of the general populace, who affectionately addresses her as "Princess Nanna".
In Chapter 7, if Nanna speaks to Delmud, she will gain one point of Luck.
In Chapter 7, if Finn is Nanna's father, she may speak to him to get 5 points of Speed after Darna is captured.
In Chapter 8, after Conote is captured, Nanna may speak to Ares to reveal the truth about Eldigan to him, and she will receive two points of Strength and Defense.
In Chapter 10, Nanna may speak to Leif at any time for 100 love points and an added bonus of three points to her HP.
In the Final Chapter, if Nanna is in love with either Seliph, Leif, or Ares, she may speak to her lover. If her lover is Seliph, he will gain 3 points of HP, while if said lover is either Leif or Ares, he will gain 3 points of Defense.
Nanna starts off fairly weak, but she does come with her personal weapon, the Earth Sword, and she can become very strong after promotion with it. It is recommended that you give her the Heim Scroll as well as other scrolls to raise her magic, as well as the Neir Scroll.
Nanna - The Queen of Nordion (ノディオンの王女 Nodion no ōjo)
After the victory at Belhalla, Nanna joined Leif in the battle to liberate Agustria. Later, she married Leif and devoted her life to helping orphans who lost their family in the war. Due to her sweetness and generosity, the citizens affectionately referred to her as "Princess Nanna" even after she became queen. Her life with Leif is said to have ended happily.
Just like Felgus, Nanna was stated to be Beowolf's child in early versions of Nintendo's official website. The identity of her father was then concealed.