The Invisible Guardian - Facts

 This trilogy is called Baztan, which refers to the area where the novels take place. Baztan is a municipality from the Chartered Community of Navarre, northern Spain. It is located 58 km  from Pamplona, the capital of Navarre.

Elizondo is where the crimes take  place. Elizondo is a town located in the province and autonomous community of Navarre. It is located on both banks of the Baztan River. The town is the capital of the Baztan valley and where most service establishments are concentrated. 

One of the elements that lead Amaia to the murderer is Txantxigorri, some type of cake. A chanchigorri cake is a Spanish pastry, common in the cuisine of Navarre. These desserts have a rounded shape. They are traditionally made at the time of pig slaughter, and their main ingredients are fried pork, lard, bread dough and sugar. They are usually served warm and are mainly marketed in the autumn months.

Amaia is from Elizondo but lives in Pamplona. Pamplona is the capital city of the Chartered Community of Navarre.

The killer is identified as the Basajaun. In Basque mythology, Basajaun is a huge, hairy hominid dwelling in the woods. They were thought to build megaliths, protect flocks of livestock, and teach skills such as agriculture and ironworking to humans.

Another element in the Basque mythology which is referred to in the novel is Mari. Mari is the main goddess of the ancient Basque mythology, who lives on the eastern slope of Mount Anboto. From there she takes care of the environment and dispenses justice. 

Some people refer to one of the dead girls, Anna, as a belagile, a witch. A belagile is someone who has powers that come from wicked spirits or the devil.  

Amaia mentions how the witches in Navarra were accused by the inquisitor Pierre de Lancré and were executed. Pierre de Rosteguy de Lancre or Pierre de l'Ancre (1553–1631), was the French judge of Bordeaux who conducted the massive Labourd witch-hunt of 1609.

Johana, the victim that is not killed by the same murderer, is Lekaroz. Lekaroz  is a village located in the municipality of Baztan.