Steward of Xiphosura
The stewards are servants of Xiphosura Kabuto chosen from mortal races. They retain more of their free will than those under the influence of an emissary, but they are also called upon to more directly carry out the wishes of Xiphosura Kabuto.
One of the purposes of Kupola appears to be the recruitment potential stewards.
Domnall Sheridan appears to have become one of these.