The Greensong is a magic Taig spell that allows the singer to run tirelessly through Taig rich areas. It does not allow the singer to run any faster than normal, but it allows them to run without stopping. The Greensong seems to have originated with the orcs.
While singing the Greensong, the singer is not aware of the passage of time. The orcs have indicated that it is possible for the singer to sing so long that they starve to death without ever realizing it. For this reason, the singer must pick a destination they are running to or a stopping trigger before they begin.
Not everyone can learn the Greensong. So far, the only two non-orcs that have been able to learn it are Rutbere the Kuakgon and Clementine, Paladin of Torres. While Rutbere is singing the Greensong, his wolf Rhaver seems to be able to run indefinitely as well, suggesting that it is sharing in the spell with it’s master. Clementine’s horse, Anne, however is not able to share in the spell and gets annoyed when forced to run without stopping.