I've been thinking recently about a slightly different way of handling deities in a campaign, moving a step away from the prototypical "god of order" ,"goddess of healing", "god of the sea" type pantheons which seem typical in fantasy games. My thoughts were partly inspired by James M's Petty Gods project. He mentioned at some point that he envisages the petty gods as being of about the same power as the arch-devils and demon lords in AD&D -- awesomely powerful compared to average mortals, but certainly not invulnerable to a well-prepared party of high-level adventurers. I like this image of gods, as awe inspiring and yet still fallible, and very far from omnipotent.
I was also contemplating the role of gods in a fantasy world -- why they want worshippers and why people want to worship them. The answer that came to mind is that 1: gods crave either power (real power in the real world, that is) or idolisation, or both, and 2: they attract followers by promising them a little bit of their power, in a variety of ways (an afterlife, for example, or progression through a religious hierarchy). The promise of an afterlife would be especially appealing if the supposed (or even proven) fate of the faithless was suitably horrible -- eternal limbo or undeath.
A third and final factor in my mental deity mix is the old AD&D rule about there being a % chance of a demon appearing when its name is spoken. I find that enormously evocative, and scary, and love the idea of extrapolating that concept to all deities. That'd lead to these powerful supernatural beings having 'true names' (which invoke their power) as well 'common names' or aliases which allow people to discuss them without risking fire and brimstone.
Put all this together and you get a world where gods potentially rule cities, regularly make appearances in person to impress their mortal followers (or at least send emissaries to do so), demand taxes, offerings and sacrifices of various kinds, and have the direct and immanent ability to respond to someone who utters their name. These gods I'm imagining are, it has to be said, mostly on the nasty side -- greedy, vain, sadistic, megalomaniac -- that sort of thing. Basically like insane emperors with the volume turned up to 11. There'd probably be a few gods out there of a more benevolent or philanthropic nature, but, as the lesson of history shows us, the most powerful leaders of the world are more often than not the most crazed and egotistical. (That's one way of looking at history anyway... I accept there are likely others. ;)
As an upside, gods like these aren't so far from mortals, and there'd be tales of great heroes defeating gods, and perhaps of literally being deified themselves.
As a specific example, here's a rough idea of the sort of god I'm thinking about.
Known as: The Cold Prince
Alignment: Lafwul Evil
Temple: Shrines to Jaaquai can be found throughout Old Aalia. His temple lies in the city of Sendak.
Demands: Jaaquai demands monthly tithes of silver from his followers and the rulers of Sendak, and threatens unending winter if they fail to comply.
Promises: The god offers loyal followers the opportunity to serve him in the afterlife in his fathomless and opulent palaces of ice. He also promises protection from the cruel cold of winter.
Followers: Devotees of Jaaquai can be recognised by the missing ring finger on their left hand, which is cut off during an initiation rite.
Manifestations: At midnight on the winter solstice a gateway opens in the temple of Jaaquai, leading into the god's ice palace. Followers are welcomed within and a great feast is served. Worshippers present gifts to the Cold Prince -- typically jewels and silver. The god chooses slaves from those present, and appoints three priests who will serve as his ministers for the following year.
Speaking the god's name: There is a 5% chance of Jaaquai responding when his name is invoked by a mortal. If the god responds, roll 3d6. Devout followers re-roll results of 15 or higher.
3: 1d6 ice devils or winter fey gate in to aid the supplicant. 50% chance of the god himself making an appearance as well.
4: An ice devil or winter fey gates in to aid the supplicant.
5 - 6: The supplicant is granted one use of one of the following spells (whichever is more helpful): resist fire, resist cold, hold person, obscuring mist, wall of ice.
7 - 8: The supplicant is blessed by one of the spells listed above, but is expected to make an offering to the god in return. Treasure worth 2% of the character's XP must be donated within a month at the god's temple.
9 - 11: The supplicant is paralysed with awe for 1d6 rounds.
12 - 13: The supplicant is affected by a slow spell.
14 - 15: An ice storm manifests, centred on the supplicant.
16 - 17: An ice devil or winter fey gates in and attacks the supplicant.
18: 1d6 ice devils or winter fey gate in and attack the supplicant. 50% chance of the god himself manifesting and attacking as well.