Trudvang Chronicles Gamemaster’s Guide, published in 2021, was written by Theodore Bergqvist, Magnus Malmberg, Anders Jacobsson, Max Herngren, and others. It is one of two core Trudvang Chronicles books: the other book is 2021’s Trudvang Chronicles Players Handbook, written by Theodore Bergqvist, Magnus Malmberg and Anders Jacobsson and others. The English translator for both books was Andovar.
Back in the dawn of time, Chaosium’s Basic Roleplaying begat Äventyrsspel’s 1982 Drakar och Demoner (in its first edition, a combination of Basic Roleplaying and Worlds of Wonder’s Magic World). After a convoluted process too lengthy to be detailed here, this led to Riotmind’s 2016 Nordic-and-Celtic-themed fantasy roleplaying game Drakar och Demoner Trudvang1, the Anglophone edition of which is Trudvang Chronicles.