lukelightning said:
But from what I hear, in FR you have to chose one specific deity to be your patron. In Eberron, even clerics worship entire pantheons (though typically just the Sovereign Host, not the Sovereign Host and Dark Six).
In the Forgotten Realms, to cast divine magic you have to have a source for that spell, and that source is a deity. This means that Clerics, Druids, Rangers and Paladins have to worship a specific deity. If they are a part of an order which worships a set of related deities, like the Order of the Long Death, then one of those deities provides spells and is their technical patron for things like domains ect. Essentially it means you can't be a cleric of an idea/concept/force/god you just made up, it has to be an actual deity that exists in the setting. If you want to be a Cleric of the Faerunian Pantheon, and offer prayers up to the pantheon as a whole, you could try, but which deity, if any, that decides to grant your spells and offers you your domains might not be one you'd like.
The FRCS says on page 290 that most denizens of Faerun worship multiple deities, or at least pay homage to various gods in appropriate situations (like praying to Chauntea for a good harvest, or praying to Lathander for a bright sunny day tomorrow), but it says most people feel at least a little preference to one deity over others, like one temple they might regularly worship at or one that is particularly relevant to their life.
The other place where is is important to have a patron deity is when you die. When souls die on Faerun, they go to the realm of Kelemvor, the God of the Dead. This serves as a sort of waiting room and processing facility. Each deity, or group of related deities, has an afterlife of their own, and various planar servants regularly visit Kelemvor's realm to retrieve the spirits of their faithful and take them on to a proper afterlife. For those who fear the afterlife of their deity (like worshipping an evil god for power in life, and then realizing what the price will be in eternity), a small number of Devils have been allowed in to try and barter deals with dead spirits, that life as a minor devil would be preferable to where they would be going otherwise. The typical person who prays to many gods as appropriate but never declared a specific patron deity is not punished, a servant of a god appropriate to their alignment and general personality will claim them.
The only people who lose are the Faithless, those who totally denied belief in the gods (what we would now call atheists), and the False, those who professed belief in a deity and their ideals but were completely contrary to them (such as publically worshipping a good god and publically proclaiming his virtues and wearing his holy symbol, but torturing and performing dark rituals and betrayals in private). Those spirits end up disposed of and turned into building blocks in his realm. The FRCS says specifically that a DM should not punish a character for not choosing a patron Deity in life.
So, in the Forgotten Realms, you have to have a specific patron to be a divine spellcaster because that's how their cosmology works with divne spellcaster, but otherwise you can pray to every god in the Faerunian Pantheon, Dwarven Pantheon, Elven Pantheon, Gnomish Pantheon, Drow Pantheon, Orcish Pantheon, Draconic Pantheon, Chultan Pantheon, Mulhorandi and Untheric Pantheon, Zakharan Pantheon, and the Celestial Bureaucracy of Kara Tur if you really want to.