Different Germanic Neopagan groups celebrate different festivals according to their cultural and religious focus. The most widely observed Heathen festivals are Winter Nights, Yule, and Sigrblót, all of which were listed in his "Heimskringla" and are thus of ancient origin. The first of these marks the start of winter in Northern Europe, while the second marks Midwinter, and the last marks the beginning of summer. Additional festivals are also marked by Heathen practice throughout the year. These often include days which commemorate individuals who fought against the Christianization of Northern Europe, or who led armies and settlers into new lands. Some Heathen groups hold festivals dedicated to a specific deity.