Interesting feature of our copy of this book: on page 285 Lee appears to refer to [the] Nulgrave as "Tarshish" as well as Nulgrave.
(First DAW printing, March 1986. DAW Collectors Book No. 665) Oh, this is handy, a google books view of the page in question. Could not seem to "Update" with the link intact, so close the spaces: http s://www.google.com/books /edition/Dark_Castle_White_Horse/DFGJEAAAQBAJ?hl=en&gbpv=1&dq=Tanith+Lee+%22Nulgrave%22+%22Tarshish%22&pg=PT269&printsec=frontcover