Translated from the designer notes on second page:
Kauhun ja pimeyden kultit (eng. Cults of terror and darkness) is a book about dangerous cults of Glorantha that has been compiled from a few sources.
The first part of the book, Kaaoksen kultit, is based on the supplement Cults of Terror, for the ancient second edition of RuneQuest. It has been used for the cosmological and historical introduction and three chaos cults, which are not found in Gloranthan kultit or other RuneQuest supplements published in finnish. Their terminology has been slightly revised to suite the third edition of RuneQuest. These long cult descriptions are no longer available in english. The fourth cult, Punainen Lepakko (Crimson Bat), is a long description revised for the third edition, made by Greg Stafford and Sandy Petersen. It originates from Tales of the Reaching Moon -issue #8.
The second part, Peikkokultit, includes descriptions of all notable troll cults, which haven't been dealt with in Gloranthan kultit or Vanhat rodut -books. These descriptions have been picked from the Troll Gods box by Avalon Hill.
The book ends in chaotic adventure, which is writen by Michael O'Brien, young and promising australian RuneQuest-writer. He's previous work, inc. Auringon Kreivikunta, have raised him in a short time as one of the big names of RuneQuest. The finnish translation of Yövalon varjossa (In the shadow of the nightlight) in this book is also the first published version of this adventure in the world.