Highwater is a spy who defected from the Cult of the Dark Sun to follow Ephrim.
History
Highwater was sent to tail Ephrim as he left Rosemerrow, keeping an eye on his movements and killing him if he got in their way. Ephrim was able to get the drop on her one night, interrogating her about her mission. Seeing that she was more impressed with his power than committed to the cause, he realized that he could sway her with his inner fire. Having convinced her to follow him, Ephrim sent Highwater to return to her church and tell them that he was dead, before coming to find him if possible and giving him information on their next move.
After the establishment of the Last University as a settlement for refugees, Highwater worked as Ephrim's retainer, notable for being the one who had served him the longest.