The Law of Surprise is a custom as old as humanity itself. The Law dictates that a man saved by another is expected to offer to his savior a boon whose nature is unknown to one or both parties. In most cases, the boon takes the form of the saved man's firstborn child, conceived or born without the father's knowledge.
Ciri came to be Geralt's ward after he invoked the Law of Surprise on Duny and Pavetta. Geralt demanded that which Duny already had, but did not know of. This, Geralt revealed, was Duny's child, carried, unknown to Duny but known to Geralt, by Pavetta. Highlighting the destiny of the relationship between Geralt and Ciri, he claims her a second time when he invokes the Law of Surprise on a traveling merchant he saves from monsters during a random encounter. The merchant is unaware that his wife has taken Ciri into their home as a war orphan.
"The first thing that comes to greet you."
When requesting "the first thing that comes to greet you", the price could be the likes of a dog, a halberdier at the gate or "a mother-in-law impatient to holler at her son-in-law when he returns home."
"What you find at home yet don't expect."
When requesting "what you find at home yet don't expect", the price could be a lover in the wife's bed, but usually a child (either newborn or still within the womb).
Involving Geralt of Rivia
- King Roegner of Cintra, as a reward to Urcheon of Erlenwald, promised him "whatever he had left at home without knowing or expecting it". This was his daughter Pavetta, for whom he officially returned 15 years later, although they had in fact already met.
- After curing him from his curse, Duny offered whatever Geralt of Rivia asked for. Geralt asked for "that which you already have but do not know": Pavetta and Duny's daughter Ciri.
- Geralt unknowingly names Ciri as his reward a second time when he saves the life of Yurga, for while the man was away, his wife took in the orphan girl.
- Geralt was thought to be a child of surprise, although he himself debunks it.
- When Duchess Anna Henrietta asked Geralt in The Beast of Toussaint regarding rewards and the Law of Surprise, Geralt can answer in a number of ways: saying that the law is something that is always done or not, or saying that the law is said from time to time.
From legends and tales
- As a child, the legendary hero Zatret Voruta was given to the dwarves because he was the first person his father met on his return.
- Mad Deï demanded a traveller give him what he left at home without knowing it. This was the famous Supree, who later liberated Mad Deï from the curse that weighed him down.
- Zivelina became the Queen of Metinna with the help of the gnome Rumplestelt, and in return promised her first-born. Zivelena didn't keep her promise when Rumplestelt came for his reward and, by using spells, she forced him to run away. Not long after that, both she and the child died of the plague.
- The bard Dandelion speaks of the Law of Surprise, claiming that "Witchers take the Unexpected Children to their fortresses and train them to be their successors."
The Price of Neutrality premium module
- When a witcher saves a man's life and the man says, "In gratitude, I will give whatever you desire," the witcher then answers, "You will grant me whatever unexpected thing you encounter when you return home." In rare instances, the surprise proves to be an infant, born during its father's absence. Based on the Law of Surprise, the child belongs to the witcher, becoming the Unexpected Child to whom the witcher is bound by Destiny. Many Unexpected Children were brought to Kaer Morhen, where they were then raised and trained to be witchers.
- In Slavic mythology, The Law of Surprise was originally a form of payment for a devil's service.
- In the book of Judges, chapter 11, Jephthah the Gileadite makes a deal with God that in return for victory over the Ammonites, Jephthah will sacrifice to God the first thing that comes out of his house to greet him on his return. As his daughter is the first to greet him, Jephthah gives her life over to God.