The battle after Nethar took his dragon form was quick and decisive. Yi Lai never even had to do anything. She just stood there, keeping her eyes on everything, watching them scream.
It was a chaotic and devastating display that left them all screaming before they succumbed to death. In the end, only Lady Oracle remained alive.
Yi Lai did say she would keep one of them, and so she saved the strongest.
She wasn't stupid; she knew that if anyone had the means to deliver her master's message to the Hand, it would be the leader of one of the world's most dangerous organizations—not anymore—but she held some authority.
To some extent, she does again, and so she knew Lady Oracle would be able to deliver Kent's message.
"Nicely done, Nethar," Yi Lai praised her only undead and then turned to the only surviving member of the Oracles... their leader.