Fenthaza is a yuan-ti leader in Omu. She is a rival of Ras Nsi's, and would like to usurp him.
She tried to ambush the Wafflecrew in Omu, but the arrival of Klauth, the red dragon, ruined her attempt.  When Diath had his nightmare vision, Fenthaza asked him to take over the yuan-ti clan. She said that his ancient soul made him powerful.