Vance planned a fourth novel Pharism: Alastor 458, but it was never written.
[1] A fourth authorised novel by Tais Teng, Phaedra: Alastor 824, was published under the "Paladins of Vance" label by Spatterlight Press in 2019.
[2] The series takes place in the Alastor Cluster as part of Vance's larger Gaean Reach fictional universe.
As described in the novel Marune, three thousand of the star systems in the cluster are inhabited by five trillion humans.
"[3] They are ruled by the laissez-faire Connatic Oman Ursht, "the sixteenth of the Idite dynasty".