Hoard of the Dragon Queen - Dragons of Faerûn
Jamna is a female gnome that the party met on the road to Waterdeep. She revealed that she was tailing the Dragon Cult to gain information about their activities and goals.
Calserra Nobleshield revealed to the party that Jamna’s true loyalty, if indeed she has any at all, are to the Zhentarim. Calserra ascertained that Jamna had tipped off Taran Moran that the adventurers who swindled his brother were in Waterdeep. Her motives in first helping and then plotting against the party are unclear.