Eunice St. Clair's book, depicting Goblins and Trolls in the Age of Fairies.
The Age of Fairies was a time period long ago when various mystical creatures, including Goblins and Trolls, lived alongside humans. This age culminated in a war when a Troll named Torok wanted to rule over the humans. (Troll)
The story about Peter and the Goblins, told by Grandpa Seth, seems to take place during this age. (Troll 2)
The events of Quest for the Mighty Sword also seem to take place during this era. (Quest for the Mighty Sword)