A Mental Cobweb in Basic Braining.
Mental Cobwebs are bright-purple colored cobwebs found in mental worlds that can only be collected with the Cobweb Duster. They form when an area of the mind isn't used for prolonged periods of time. Those who are labelled insane have cobwebs that can get so big that they block off larger portions of their mind.
Story
The first cobweb is encountered in Basic Braining, where Coach Oleander tells Raz to steer clear of them at the moment, as they cannot be removed without a Cobweb Duster, an item available for purchase at the Camp Store. Once a Mental Cobweb has been extracted, Raz can travel to Ford's Sanctuary and use the loom to weave the web into a PSI-Card.
Cobwebs hinder player progression from the Milkman Conspiracy onward.