One of the seven barae, the Chosen of Ubtao

A former Bar'ae, an immortal defender of Mezro. He was tasked to defend the city from all threats, Ras is a title akin to Duke. Nsi was a paladin, a chosen one of Ubato. He betrayed his oaths, saja doesn't know how or why, he was banished fell from paladin hood becoming a warlord. He raised an army, he sought revenge. his powers were stripped of him, his immortality and divine powers. When he lost these he lost control of his army..He found shelter in an ancient and lost city called Omu.
He seeks revenge still against Ubato and chult, he seeks damage against those who cast him out. He searches to bring forth Dendar the night serpent.

 
@Sajwants us to kill Ras Nsi. "How would we stop him?" - No clear answer, he is embedded in Omu. She has limited knowledge, but within Omu is another great danger. He is trying his best to bring back Dendar.

 
Ras Nsi sought out the support of the Yuan-ti, and he has managed to gain influence and power within the Yuan-ti in some manner. Nsi is somehow stopping Mezro from returning, it cannot come back to this plane until he is vanquished.

 
When he pushed back the tribe Waring with mezro, he chose to chase them down after they retreated and wiped out every man woman and child. He was the most powerful of the Bar're and used the powers he was given to bring back the dead, manipulating it to raise the dead.