- MRR... MRR... RRR?
The Fun-Sized Mobile Agony and Death Dispensers are powerful animal-shaped clanks inside Castle Heterodyne. They were created by an unknown-at-this-writing Heterodyne as not unlike the Torchmen, to patrol the Castle interior, providing rapid remote access anywhere inside the complex, and efficient dispatch of unwanted visitors.
When Agatha arrives in the Castle, they are Devil Dogs by the other residents even though they have a feline appearance (Even the Foglios call them "tiger-like".). The novelization rewrites this scene to have Moloch call them Steam Cats. They are very likely given other labels by the prisoners, but this is, after all, a family-friendly semi-fictional historical romance and such names are not appropriately printed here.
Among the features one might expect from a generally feline physiognomy, the Fun-MADD has a scorpion-like tail which provides defense for its own dorsal area; and self-luminous eyes and mouth, which could possibly be providing infrared illumination as well as systems heat exhaust.
Normally these clanks are controlled universally by the Castle, but when Agatha encounters her first example of one, they are operating independently due to the building's widespread damage and system disconnections. In this state they are, able to hunt only by detecting motion, and are , but are still physically powerful. Why they are still active after twenty or so years with no maintenance is not explained; despite being the size of a wagon, they have no obvious source of power. Perhaps they draw power from Castle systems.
Agatha deals with that first example by luring it into an area where a compliant Castle-fragment can crush it, but when she later encounters a whole swarm (pack? clowder?) of them, instead of just using the handy Heterodyne Harvester to do the job herself, she creates a temporary bridge to bypass them. At another point she has some Dingbots hotwire a damaged one and uses it to settle Zola's hash, at least temporarily.
When the ascendant Lady Heterodyne and her various friends and minions finally succeed in fully Otilia into an FSMADD, she also can . This is fortunate, as the aforementioned bridge plan gets disrupted by unforeseen events, and Otillia arrives just in time to save Gil and Tarvek from being Devil Dog chow.The Castle's power, it is able to reassert control of the FSMADDs. Additionally, after some of Team Agatha the consciousness of Muse of Protection