The Dieter Eagan National Forest is a forested wilderness area in Kier, PE, named after Kier Eagan's twin brother, Dieter Eagan.
The area contains several landmarks, including Scissor Cave, where Kier Eagan was said by Seth Milchick to have tamed the Four Tempers, and Woe's Hollow, where Kier claims to have met the Temper Woe for the first time. It also contains a lake overlooked by a rocky promontory, which resembles the scene depicted in the Kier Cycle painting Kier Invites You to Drink of His Water.
During the Lumon Branch 501 MDR team's ORTBO in the forest, they encountered what appeared to be the decayed carcass of a seal lying next to a river; the circumstances surrounding this finding remain unknown.