The Spider Guild was a selection of people chosen by Atury to infiltrate local society of Errod for the purposes of collecting information and obtaining positions of power. This was his first priority, as he saw the importance of gaining an understanding of their new environment. He selected Chryale Jacinth to lead this task.
Dreadgate Lore
This faction corresponds directly to the Artifice Craft in Dreadgate (TCG), also known as the black or grey deck.
Canonically, the units in Artifice are called the Spider Guild. This is in reference to their reputation as thieves and cutthroats, spies, etc. Given that Atury is the de facto leader of the Sorcery craft, and that he has an affinity for the Spider Guild, artifice is most compatible with sorcery. When Atury was a child, his father was tricked into selling him to a traveling circus called Circus Nomadia Supernal. It was there that he learned the arts of trickery, sleight of hand, deception, etc. Because of this, he embraces those in the Spider Guild, and he understands how to maximize their skills.
Upon arrival on Errod through the Dreadgate, Atury immediately knew he would need every advantage to stay alive and one step ahead of the Green Legion. He also knew he would need intelligence on the geography, culture, language, etc. of the strange place they now found themselves, so he leaned heavily on the Spider Guild to infiltrate all aspects of the local landscape. Unfortunately for Atury, the opposition understands their value as well, and they sometimes leverage the Spider Guild for their own advantage.