The Most Difficult Single Class Campaign

I've long been interested - really since I was an adolescent reading the old 2nd edition 'brown book' Complete... series - in the idea of a single class campaign. There is something that is simply innately appealing about its combination of challenge (how would a party of 1st level Magic-Users navigate the problem of combat?) and possibility (what type of world, setting, scenario is appropriate for a party of Magic-Users to exist within?).

Some classes are, however, much easier to single-classify than others. Fighters, for example, seem ready made for it - a single class fighter campaign would correspond pretty closely with the presumptions of a traditional sword-and-sorcery setting of the Conan variety, not to mention of the Greek myths (what is the Odyssey or the legends of Theseus or Jason if not single-class fighter campaigns?). 

Thieves are another easy sell - the PCs are a gang of assassins, tomb-raiders or burglars; they are perhaps members of a guild....a single-class thief campaign almost writes itself and, like the single-class fighter campaign, has a ready-made implied setting (an archetypal Big Magical City).

Other, more specialist or optional classes, likewise seem tailor-made for 'Everything Is...' campaigns. Everything is druids = PCs are protectors of a pristine natural region against interlopers. Everything is paladins = PCs go around smiting evil or protecting against demonic or undead interlopers. Everything is rangers = PCs are responsible for the guardianship of a vast border region or badlands, etc.

The most difficult single class campaign to conceptualise and sell is, I think the single class cleric campaign. This is for two reasons. The first is that clerics are, stereotypically, like the goalies or bassists of D&D. They are necessary but their roles - protection and healing - are unglamorous and even dull. The second is that a single class cleric campaign is hard to envisage without too much of an overlap with other single-class campaign motifs. If the clerics are going around fighting demonic entities or the undead or whatever, how is that different to a single-class paladin (or fighter) campaign? If they are scouring the world for holy artefacts, how is that different to a single-class magic-user campaign? And so on.

The route forward for a single-class cleric campaign would be I think to focus on two things. First, it would be necessary to pay careful attention to the institutional environment in which clerics are situated. Whether the medieval warrior-priest of OD&D archetype or a heart-ripping Aztec thaumaturge or jungle witch-doctor or steppe shaman, a cleric is part of a broader religious infrastructure. A single-class cleric campaign would thus have to I think be centered around the furtherance of the ends of an order of some kind and may therefore concern, to a much greater extent, an idea about the systematisation of internal politicking and perhaps also the extent to which there are theological rights and wrongs. 

Second, it would be necessary to clarify what a gang of clerics would be motivated by. 'Quest-dispenser' campaigns are boring and railroady - I would not be an advocate of 'mission of the week' style adventuring in which a holy oracle of some kind simply declares tasks for the PCs to carry out. What then would clerics do?

Some possibilities:

• Pilgrimage - a long journey across a pre-defined and dangerous route.
• Protection of a religious minority - perhaps the PCs are clerics of a religion that a specific, relatively small group of people hold dear against a majority that is indifferent or vaguely hostile
• Roaming about applying holy law in a quasi-Dogs in the Vineyard format
• Tending to a flock of believers in far flung places scattered across a vast landscape filled with mystery and terror 
• Searching for sacrificial victims of a particular (rare) kind

The trick is pulling this off in such a way as to avoid 'quest-dispensation' and maintaining - and making maximum use of - the specific role of clerics as such.