One group of Unkin see themselves as Angels, and have set up a Covenant promising to reject any ancient deity looking to regain his or her past glory; they are at the time of the narration getting ready for a final war.

A group of newly born Unkin (one can become an Unkin through certain unspecified events in his or her life) who refuse to take part in such war are the main characters: Seamus Finnan, an Irish angel hiding out in the desert; Phreedom Messenger, a trailer park biker trying to avoid conscription; Thomas Messenger, her gay brother who is trying to disappear into the Vellum where he will never be found; Jack Carter, a Covenant spear-carrier sent to kill Thomas but in love with him.

[5] The seven main characters are archetypes of characters from myths and legends: Jack, also known as Jack Flash, Spring Heeled Jack, Iacchus and Captain Jack Carter (a legendary World War I hero in one of the parallel worlds in which the novel is set), also inspired by Luther Arkwright and Michael Moorcock's Oswald Bastable and Jerry Cornelius;[6] Thomas Messenger, also known as Puck, Tamuz and Matthew Shepard; Phreedom Messenger, known as Anna, Anaesthesia and Inanna; Guy Fox, who is also Guy Fawkes (although closer to his representation in V for Vendetta than to the historic character), Guy Reynard and (the Prussian Baron Reinhardt); Joey Pechorin (also Joey Narchosis and Judas) Don MacChuill (also Don Coyote, Don Quixote) and Seamus Finnan (Shammus, Finnegan, Prometheus, Samuel Hobbsbaum, Sammael).

[7] From a psychoanalytic point of view, the seven main characters can also be seen as the Super-ego as guiding conscience (Guy/Reynard), the wild and libidinous Id (Jack), the Anima and Animus as a triple goddess/god figure (Phreedom), the “inner child” of the Self (Thomas), the Ego that has to deal with society and reality (Seamus), the Shadow as the dark side (Joey), and the wise hermit or old soldier as an image of age and experience (Don).

[22][23][24] Vellum has been translated into German by Hannes Riffel,[25] Finnish by Nina Saikkonen,[26] French by Florence Dolisi,[27] Italian by Stefania Di Natale,[28] Spanish by Luis Gallego Tévar[29] and Polish by Anna Reszka.