Aquatic people with tsars, princesses and a castle Carl intends to assault tomorrow night.
The naiad come up entirely through Samantha's claimed genealogy. She names Princess Yungsten of the Naiad as Signet's grandmother, which by her arithmetic makes Signet her own third cousin thrice removed — with the concession, when Carl presses, that it is really by marriage, since Yungsten's line runs back through a Tsar Guggenheim who married in. Carl cuts the lecture off before the family tree resolves.
What the exchange establishes is that the naiad are a titled people with tsars and princesses, that Signet holds the rank of tsarina among them, and that they have a castle — one Carl and Princess Donut plan to assault tomorrow night, when they will see Signet again.
Not described here; known through their titles and their castle rather than their bodies.
An aristocratic aquatic people whose tsarina Carl is negotiating with and whose castle is his next objective.