"There's nine of them," Magnus says, promptly. "Asgard is where the Aesir gods live, and is closest to the tree's canopy. The Aesir are the more warlike ones? The Vanir are the nature gods and they live in Vanaheim. Um, the heroic dead that Odin, the head honcho of the Aesir, claims? They go to Valhalla, which is mostly in Asgard but can touch the other worlds. The heroic dead that Freya, my aunt, claims go to Volkswagen---no. Sorry. Folkvanger. I always get that one wrong. Folkvanger is mostly in Vanaheim. Anyway, Alfheim is where the light elves live, and it sucks there. Talk about lawmen! Midgard is earth, where the humans live, and it's in the middle of the trunk. Giants are native to Jotunheim, dwarves come from Nidavellir -- that one is in the roots. Muspellheim is the world of fire, where the fire giants and demons live, and Niflheim is the world of ice and snow -- it's too cold even for me; I almost died there once -- and Helheim is the underworld where the dishonorable dead go."