When he is captured, Ransom discovers that his purpose is to serve as a 'ransom' for the entire human race, allowing Weston and Devine to continue their explorations of the planet Malacandra (Mars).
Some casual references in Perelandra reveal that he had fought in the First World War, that he had been on the Somme, and that on one occasion he had to overcome considerable trepidation before accepting - and successfully implementing - an unspecified "very dangerous job".
It is also mentioned that, at some later point in his life, he had "to screw up his resolution to go and see a certain man in London and make to him an excessively embarrassing confession which justice demanded"—which Ransom eventually did, and of which no further details are given.
A professor at Cambridge, he is highly regarded, even by his enemies, who in That Hideous Strength mention him as among the topmost in his field, noting that, but for his Christian convictions, he might have rendered very useful service to their cause.
After his sojourn on Malacandra/Mars, Ransom is mentioned as staying for a prolonged period at a cottage three miles outside "Worchester", having evidently left temporarily or permanently his Cambridge job.
While on Venus, Ransom becomes in effect a prophet in the Biblical sense—i.e., a person to whom God speaks and on whom a specific Divine command is imposed (and who, like Jonah, strongly resists and makes a considerable effort to avoid, before bowing to the inevitable).
The wound may refer to Genesis 3:15, where God curses the Snake for his tempting of Eve and causing the Original Sin: "And I will put enmity between you and the woman, and between your offspring and hers; he will crush your head, and you will strike his heel.
He has become too much of an august and hieratic personage, seen mainly through the eyes of the book's female protagonist Jane Studdock, who falls in love with him [1] — hopelessly, as she realizes from the start, especially since he is an unwavering upholder of the sanctity of marriage and clearly wants her to be reconciled with her estranged husband.
In the end, Ransom's role as a saint or prophet is enhanced by his being taken alive into Heaven (actually, back to Venus/Perelandra), an honour reserved only to a very small handful of particularly deserving Biblical and mythical characters.
As is true with most of Lewis's writing, The Space Trilogy has religious symbolism in which Ransom takes on the role of a prophet preparing for the end times by resisting demonic forces on Earth and Perelandra.