Unlike many sects, the Guild has a specific local purpose - although "local" in this context refers to all of Limbo. The sect is virtually unknown outside that plane, because its sole purpose is to train anarchs in the use of the chaos-shaping proficiency. And since chaos-shaping only works on the churning matter of Limbo, there's little enough reason for chaos masters to leave. They are valued by the other dwellers of Limbo, not counting the slaadi, since they make sure dwellings and solid ground continue to exist.
Those interested in chaos-shaping should be aware that in the hands of a highly trained master, this skill may produce remarkable results. Thing is, the Guild is strictly a githzerai institution. Given the nature of the insular race, it's rare that any berk from another race learns the true dark of chaos-shaping.