Pustules are (relatively) heavyweight subpuppets. They are spawned by Reconcilants as a mix of heavy area damage and support for Imps. A group of Pustules is known as a clump or a clot.

As far as subpuppets go, Pustules are quite large, standing at 2' 8" (81cm). This massive size causes them to be mistaken for regular puppets occasionally, but as they are spawned from Reconcilants, they are in fact subpuppets. This size is represented in their psionic weight usage; Pustules are "heavy" subpuppets, using roughly twice the psionic weight of an Imp or Array. While Pustules sometimes appear to lack any distinguishing traits at first, the large blister sacs on their back are their defining feature. These blister sacks get far larger than any normal puppet's (with one sac occasionally exceeding 10% of the Pustule's body weight), and are crucial to the Pustules' role, both offensive and supportive. Internally, Pustules have excessive tissues dedicated to producing their bile-like acid, and are one of the only subpuppets to sport redundant organs.

Pustules have a surprising variety of available actions in combat, given their simple body plan. They can spit their acid directly as a short-ranged chemical attack, which is their primary method of dissuading foes. If Imps are present, the Imps may coat their talons in the Pustules' venom, adding a thick acidic coating to their assaults. Lastly, if a Pustule is cornered or surrounded on all sides, it may inflate one of the large blister sacs on its back. The subsequent explosive rupturing damages the Pustule, but splatters a heavy dose of acid across anything within a roughly twenty foot radius.

In combat, Pustules secrete a mixture of pheromones that increase the combat effectiveness of nearvy Imps and Arrays. This pheromone usage is unique exclusively to Pustules; even Reconcilants rely on magic to effuse their healing auras. Why Pustules uniquely use chemical communication to enhance their allies as opposed to some psionic or magical method is believed to be linked to their relatively simple body structures, and suggests an adaptation of normal chemical secretion glands (similar to how acid-producing tissues are derived from sebaceous glands) is responsible for much of the Pustule's combat support.

Pustules spend much of their time lazing around or grazing outside of combat, though they are a favourite conversation partner of Imps. Given their self-sacrificial tactics, it is assumed this behaviour is to facilitate rapid replenishment of body resources and regeneration of tissues. If a Pustule has recently ruptured one of its blister sacs it will be extra sedate, and will generally not leave the side of its host Reconcilant, and will often enjoy increased first-aid attention from Deltas.

Relative even to Imps, Pustules have extremely simplistic epigenetic profiles. This is self-evident, given they have a minimal amount of unique features. However, like many venomous species, Pustules boast a robust resilience to their own acid, and the presence of a Pustule seems to act as an epigenetic trigger of its own, as Hyacinth and other puppets display better acid resistance when Pustules are present. Triggering epigenetic changes was thought to be a feature exclusive to Hyacinth or external factors, so it is believed this ability is why Pustules are otherwise as uncomplex as puppets get.

Pustules were added as part of the "second batch" with Deltas and Howitzers, added as part of Hyacinth going from an individual to a species with a corresponding Dungeons and Dragons class. Pustules were added as something heavy for Reconcilants to spawn; heavy combat-support units that interacted with Imps and could take their opponents down with them if push came to shove.

Pustules are probably the most obvious reference to the original Cataclismo inspiration for Hyacinth's character; they're heavily based on that game's "Blister" enemy, who were chunky, durable units that didn't do much direct attacking but exploded upon reaching anything unfriendly.

Pustules were kind of the first "complicated" puppet. At the time of their introduction, Deltas and Howitzers were very simple (Howitzers still are, really), but Pustules were born fully formed: Their acid spit, self-detonation, and even their interaction with Imps were all written into them from the get-go. This has given them a static, but very strong identity, though admittedly their relatively minimal interaction with Arrays dilutes them slightly.