The first scholar to write about Narjis as the mother of the twelfth Imam was Al-Masudi. According to his account, she was a Roman princess named Narjis. Ibn Babawayh was the first scholar to discuss the nationality of Narjis on the authority of Muhammad bin Bahr al-Shaybani, who attributed his narration to Bishr bin Sulayman al-Nakhkhas. According to Ibn Babawayh and Allamah Majlesi in al-Ghaibah, she was a Christian convert to Islam. Narjis was the granddaughter of a Roman Caesar who was a descendant of the Apostle Simon. Mohammad Ali Amir-Moezzi, in the Encyclopædia Iranica, suggests that the last version is "undoubtedly legendary and hagiographic". However, nowadays almost all twelvers consider her to be a Roman princess.
Saiyra, Narges Khatoon, Katrina, Lilliana and Magdalena are names attributed to her in the sources. According to the Sibt ibn al-Jawzi and Ibn Talhah, Sunni narrators, she had been known as Susan.
According to Ibn Babawayh's account, Narjis saw Mary, the mother of Jesus, and Fatimah, the daughter of Muhammad, in her dreams on fourteen nights. They asked her to become Muslim and travel to Medina by masquerading as a captive of the Muslim army. According to Al-Ghaybah, after conversion to Islam upon the request of Mary and Fatima, she had another dream in which she visited Hasan al-Askari, the eleventh Shia Imam. The Imam tells her that her grandfather will shortly send an army to fight against Muslims and that she should turn herself in as a captive without being identified.
According to Donaldson, Ali al-Hadi, Hasan al-Askari's father, wrote a letter and handed it to his friend Bashar ibn Sulaiman with 220 dinars in a red pouch. He asked Bashar to go to Baghdad where slaves were sold to inquire of Amr ibn Yazid about a slave girl who would shout in the language of Rum:
"Even if you have the wealth and glory of Solomon, son of David, I will not turn to you. So save your wealth!"
Ali al-Hadi had predicted that the slave seller would respond that in any case he would have to sell the slave girl but she would respond: "Don't rush and let me select the buyer". Bashar narrates that as per Ali al-Hadi's request, he handed the letter to the slave girl. The girl read the letter and cried. Then she asks Amr ibn Yazid to sell her to the writer of the letter, "for if you refuse I will surely kill myself". Bashar narrates that on their way to Samarra, the girl kisses the letter frequently, rubbing it on her face and body. When Bashar asks her about the reason, she replies: "May the offspring of the Prophet dispel your doubts". After a while she reveals to Bashar her dreams and her escape from her father's palace. After joining Ali al-Hadi, he invites his sister, Hakimah Khātūn, and says to her about Narjis: "she is the wife of Hasan al-Askari and mother of al-Qa'im.