On the 11th day of the Blue Moon of Year 439, an army of Frost Giants descended from the pass and attacked the Hidden Vale. Sometime during the chaos, rockfalls opened up new paths up the mountain. The party that gathered to defeat the invaders discovered the pass by chance and proceeded to climb to the top. The ascent was fraught with many deaths, due in part to the large army of Frost Giants present. The army was destroyed, however, and the population of the ice creatures soon reached a steady equilibrium.On the 51st Day of the Blue Moon, Year 439, Jedd discovered the Duldrus pass whilst searching the area for any new paths opened up by the recent rockslides. He called on Charonia and Boric to help explore the area, but the three were eventually turned back by the dragon. Not yet realizing that the pass connected to the Hidden Vale, they christened it "The Serpent's Spire".
Since the original invasion, the forces of ice have gathered to attack the lands below on two occassions. The first was on Day 228 of the Fighting Moon, Year 440, on the Duldrus side. The attack was a direct result of the return of Vandrovic with the Ice Spirit. The second time was on Day 78 of the Harvest Moon, Year 441, on the Hidden Vale side. This invasion was repelled with the help of Troll Chieftain Koggar.