Yggdrasill is perhaps the best Viking rpg that I know of. Focused on bringing both historical and fantasy elements of the culture to life, the game has earned nothing but praise from me in my earlier review of the corebook.

The Nine Worlds is the first supplement to the game, and expands the setting in a way that many fans have been waiting for. The Nine Worlds contains information on the more magical realms of the Norse setting, discussing each one in turn and giving information on the creatures and challenges that the player characters may encounter there.

The book goes into detail into all of the Nine Worlds: Asgard, Alfheim, Vanaheim, Jotunheim, Nidavellir, Svartalfheim, Muspelheim and Niflheim. The worlds receives a description of it's geography, the dangers found in the world, the occasional important location, and plot hooks and artifacts that the GM could use to spice up their Yggdrasill campaigns.

The book also has new options for player characters, the most compelling of which would have to be the option to play Half-Breeds, those born from inhuman parents. The range from the Half-Jotun, to Half-Alfar. They also special traits that influence their starting abilities.

Special powers are also covered in the book, and can cover the various powers and abilities that can be bestowed to the players via magic items.

The book also contains 3 adventures, Winter's Fall, The Hunter and The Forgotten Oath, all of which can be used as part of an ongoing campaign.

Overall The Nine Worlds is a good follow up to Yggdrasill. The book expands the setting but doesn't lose it's touch with the historical feel. Fantasy elements are sufficiently fantastic, but also well grounded in the cultural context of the setting.

If you're looking for more ways to make Yggdrasill even more compelling, then you should definitely pick up a copy of The Nine Worlds.