Back Cover: Part Three of the epic Horned Lord and Moon Sow Campaign.
From the introduction (spoilers):
Welcome to The Ragnarok Book, the third adventure in the Horned Lord and Moon Sow campaign for the Slaine roleplaying game. In this epic adventure, the heroes will deal with the consequences of civil war in their home tribe the Fir Domain, bring the tyrant Osdann to some form of justice at last, find two more of the magical Teeth of the Moon Sow, and quest for their lost tribal treasure, the Silver Sword of the Moon.
This adventure is intended for 61h level characters from the Fir Domain tribe. It would suit a party composed mostly of warriors, with perhaps one druid or witch or thief. An all-warrior party could complete the adventure so long as they have a wide variety of skills. Ideally the party should have completed the first and second adventures in the campaign, The Invulnerable King and The Teeth of the Moon Sow, but notes are included for player characters who have not played in those adventures.
All you need to play The Teeth of the Moon Sow (sic) is this book, a copy of The Player’s Handbook, and the Slaine RPG. The fist Slaine supplement, Tir Nan Og, would be useful for additional background but is not essential; the same is true of the Fir Domain sourcebook.