Originally these odd bugs were designed by alchemists to be a sort of living potion mixer. Now that the lab in which they were created has been abandoned they wander the island in search of new ingredients in which to brew potions. The potions they create are grown within their own bodies in the form of boils growing from their backs. These boils form after the Crawler has consumed suitable ingredients. However, despite making these potions the Crawler is unaware of their actual effect. That is of course until they grab the potion boils off of their backs and test it out themselves. It seems that the type of ingredients the Crawlers consume has an effect on their behaviors. With more healing ingredients rendering the Crawlers becoming more docile but poisons causing aggression within the species.