Giant Spyders were the first monsters that Kass unleashed on Meridell during his war with them.
In the original Neoquest, two forms of giant Spyders roamed the Desert of Roo in Ancient Neopia. They were named the Giant Dust Spyder and Giant Sand Spyder, and looked like this:
The Giant Sand Spyder returned in Neoquest II, kept animated by the magical power of the city of Phorofor. It protected the city, attacking travellers who ventured near. In this appearance, the Sand Spyder had the looks of a Dust Spyder.
They later appeared in the Secret Tunnels of Portal City in Treasure Keepers, but with a more traditional, non-sand look, like this: