Sanitary Legion

The Sanitary Legion, first encountered in The Science of Discworld IV: Judgement Day, is the paramilitary uniformed arm of the Omnian Church. They apply themselves to brass band practice and Good works, such as feeding the hungry, providing beds for the homeless, and communicating the good news of Om via rattling collection boxes in Pubs and selling such worthy tracts as the Unvarnished Truth and Battle Call!.

It is entirely possible this is the current mutation of the Divine Legion of old, who seeing no future for evangelising the word of Om at spearpoint after the Brutha Reformation, opted to transform itself into something less ostensibly warlike in order to ensure a continuing existence.