A shalankhkai was an advocate for the process of T'Kal-in-ket.
The original Vulcan term was sha-set, but after the reunification of Romulans and Vulcans, the ancient Romulan designation of shalankhkai was used.
By the 32nd century, only sisters from the Qowat Milat could serve as shalankhkai.
In 3189, after Michael Burnham invoked T'Kal-in-ket, her mother was assigned to be her shalankhkai, as she had taken a particular interest in the case. (DIS: "Unification III")