The first appearance of a gnoeals is during the Glorious Memories quest, in the Rellekka Hunter Area Dungeon. They are responsible for turning Nial Swifling and King Vargas into yeti and supposedly turn all adventurers they meet into yeti with the green goo that they spit. The speed at which they transform is relative to the exposure. Nial was hit by the brunt of the attack and thus transformed immediately while Vargas was only hit by a small amount and so he was able to stave off a full transformation for many years.