In House of Zeor (1974), Lichtenberg devised a future world where the human race has mutated into two symbiotically linked groups. ""Gens"" generate a sort of energy-field called selyn, which their own bodies cannot use. ""Simes"" produce no selyn, but have developed special organs to drain it from Gens in order to sustain their own metabolic functions. At one time this process was invariably fatal to Gens, but a certain painful measure of control has been achieved. The idea ingeniously combines elements of vampirism, ecological interrelationships, and sexual climax. It is studiously reinforced--or encumbered, depending on your point of view--by a made-up technical vocabulary which produces things like ""near as I can figure, it was a primary-system entran complicated by all the transfer aborts I've been having lately."" Unto Zeor, Forever takes up the attempt to regulate Sime-Gen dealings through an organization called the Tecton, which trains gifted Simes as ""channels"" and Gens as ""donors."" Digen Farris, official head of the powerful House of Zeor, is a Tecton channel who also wants to qualify as a surgeon in order to bring Gen medical resources to the Simes, still largely isolated by the stigma of their condition. He is hampered by Gen prejudice, Tecton bureaucracy, and the passions of the anti-Tecton Simes of the ""Distect."" Lichtenbarg is a pretty good plotter and a fair (if often clumsy) writer, but she'd he much better at both if she could achieve more distance from the fertile clutter of her invention.