A guild of serious men with grubby coats, hats with candle stubs on, and sacks in which things are struggling. Highest honor to guild members: the Golden Mallet. The Guild charges a high rate for pest termination, and Guild enforcers try to make sure that only Guild members are allowed to work on ratcatching. Wee Mad Arthur, a gnome and an independent ratcatcher, often has to fight with the enforcers (see Feet of Clay).
The Inner Circle of the Guild passes on secret lore, such as the possibility that rats have their own parliament, and that there is such an entity as the Death of Rats who may manifest Himself to His earthly helpers (ie, very good rat-catchers) in thanks for their labours on His behalf.
This latter proposition is almost entirely correct and almost entirely misleading, for as Mr Pounder discovers, the Death of Rats does indeed manifest to ratcatchers in certain precisely defined circumstances: ie, to collect their souls when they are dead, and to usher them through the revolving door that says REINCARNATE AS RAT UNTIL FURTHER NOTICE.
As for rats having a parliament, this has been proven correct too, at the climax of The Amazing Maurice and his Educated Rodents where Rats and Humans agree to democratic co-rule in the aptly named Rathaus.
Quite possibly members might feel the urge to attempt a Rat King out of eight pints of bravado.