Little is known about Lorelei, the patron goddess of Teuran, because the patient known as Z was not such a believer in the religious beliefs of his fellow Teuraneans.
The symbol above is a clean version of the patient's sketch of Lorelei's symbol, on banners hanging from a temple, built in her honor. The patient described that this temple is next to the school, that Zack attended in Teuran.
The original version can be found in the first Journal: Soulfire.
Her face can also be seen in the logo of the Royal Guard of Teuran (as seen in the artist's rendition of the patient's description).
As explained in the second Journal: Resolution, this symbol represents the three things that a RGT soldier protects. Lorelei's face represents the women's council, whom they serve, while the wings represent the liberties that every man, woman, and child in the city is free to seek out. The rose in the middle represents the townsfolk, the primary concern for every citizen of the Silver City. This was the legacy that she had left behind, that each citizen in Teuran was responsible for every other citizen in return.
The members of the RGT proudly wear her image on their armor, as a reminder that they themselves are the mightiest protectors and keepers of Teuran.