Ilbranteloth
Explorer
The 1e description of the Cleric class conveys minimal setting assumptions. It says:
"
The cleric is dedicated to a deity, or deities,
and at the same time a skilled combatant at arms.
The cleric can be of any alignment (q.v.)
save (true) neutral (see Druid hereafter) alignment,
depending upon that of the deity the cleric serves.
"
‘The cleric can be of any alignment.’ But. It depends on the deity. If there is only one deity, then its clerics must correspond to its alignment.
It doesnt say, every setting must have clerics of every alignment.
Rather, if a setting only has one ‘deity’, then possibly only some alignments are available.
Except the DMG clarifies it more. "Each cleric must have his or her own deity, so when a are player opts to become a cleric (including a druid), you must inform them as to which deities exist in your campaign milieu and allow the individual to select which one of them her or she will serve. This will not necessarily establish the alignment of the cleric, so at the same time the cleric player character should also state his or her ethos (not necessarily to the other players).
Furthermore, there are assumed to be evil clerics that will be NPCs against the PCs.
And that still doesn't resolve the fact that almost all clerics are dedicated to a deity. That sentence doesn't tell you anything about the religion itself - it could be monotheistic or polytheistic. It's the other sentences that address the nature of the religion - the ones that state "gods."
According to the description of the Druid class, the trees grant the Druid spells. The trees are treated as ‘deities’. But these trees are actual literal trees. They are nonhuman and ‘think’ as trees think. Specifically, the ‘mistletoe’ plant ‘gives power to their spells’ in order to protect other ‘plants’. This 1e description of the Druid is nonpolytheistic. It is animism.
"
Druids ... hold trees (particularly oak and ash), the sun, and the moon as deities.
Mistletoe is the holy symbol of druids, and it gives power to their spells.
They have an obligation to protect trees and wild plants, crops,
and to a lesser extent, their human followers and animals.
"
1e Druid engages ‘nature worship’ in the form of vegetative animism.
Which attributes deific power in such things. But furthermore, the DMG (via the index) directs you to pg 38-40 for casting, acquisition, and recovery of druidic spells. The sections included are cleric spells, magic-user spells, and Illusionist spells. There is no separate section for druids.
Druids, being a subclass of clerics, who are also called out in the second paragraph (quoted above), regain their spells with the same rules as clerics in that section.
That is, sixth and seventh level spells are granted directly by their deity, and if they have not been faithful, they can be withheld. Even third through fifth level spells can be withheld by the minions of the deity.
Mechanically, whether it's a being someplace else, or the plants themselves, they are a deity. An intelligent entity that can judge and choose to provide or withhold their blessings.
Regardless of whether you assign deity status to the druids, they are worshipping something other than the god of the cleric (assuming it's a "monotheistic" campaign).
What is the reasoning for clerics in your monotheistic campaign that druids worship and receive divine powers from the plants? That they are not gods? But the denial of the divinity of the plants does not preclude the druids for declaring them divine and continuing to receive their divine gifts.
What about the clerics, shamans, or whatever of orcs, elves, drow, giants, and evil humans? Do their clerics worship the same good god of your clerics, but are simply rewarded with spells that harm?
In our world Hitler was a "Christian" but not in any sense that I understand. But the fantasy world is a bit different. If Hitler received clerical magic, how could that be from the same god as the allies?
Regardless, if you can accept the nature (pun not initially intended...) of druids while maintaining it as non-polytheistic, then why can't use accept the different domain clerics of 5e without invoking polytheism?
That's what I'm still struggling with. Because as best I can tell, in the 5e PHB, outside of the appendix, this is what it has to say:
"Clerics are intermediaries between the mortal world and the distant planes of the gods. As varied as the gods they serve, clerics strive to embody the handiwork of their deities."
"Divine magic, as the name suggests, is the power of the gods..."
"The gods don't grant this power to everyone who seeks it..."
"...the ability to cast spells relies on devotion and an intuitive sense of a deity's wishes."
"...wade into melee with the power of the gods on their side."
"...carrying out their gods' will..."
"...the most important question to consider is which deity to serve and what principles you want your character to embody. Appendix B includes lists of many of the gods of the multiverse. Check with your DM to learn which deities are in your campaign."
Under Divine Domains
"In a pantheon, every deity has influence over different aspects of mortal live an civilization..."
"For example, the portfolio of the Greek god Apollos includes the domains of Knowledge, Life, and Light.
"Apollo, for example, could be worshipped in one region as Phoebus ("radiant") Apollo...Apollo Acesius ("healing")..."
"Each domain's description gives examples of deities who have influence of that domain. Gods are included from the worlds of..."
Each domain has a paragraph that generally starts with "The gods of knowledge..." with examples.
Outside of this quoted text, and the blurbs at the start of the domains, there is nothing that I can see that is requiring you to use a polytheistic religion. So that's a total of around 20 sentences that actually include the word "gods" or "deities" in the entire book.
But there's another major consideration in terms of presentation.
I'll rewrite the first quotes from above. I suspect this would offend a great many people, and also bring a lot of unwanted attention to the game (again).
"Clerics are intermediaries between the mortal world and God. Clerics strive to embody the handiwork of God."
"Divine magic, as the name suggests, is the power of God..."
"God doesn't grant this power to everyone who seeks it..."
"...the ability to cast spells relies on devotion and an intuitive sense of God's wishes."
"...wade into melee with the power of God on their side."
"...carrying out God's will..."
The added fluff in 5e is to help explain the concept better, and tie you closer to the worlds of D&D. Both worthwhile goals. While there may be many home-brew worlds out there, they aren't there to tie the game to your home-brew. Their purpose is to present a complete set of rules that anybody can pick up and play, and they release APs for them to play using those rules. It's also obvious that this is a game, not a real treatise on religion, and that's exactly what they want.
You could also go to the "his or her" approach by saying:
"Clerics are intermediaries between the mortal world and their deity or deities. Clerics strive to embody the handiwork of deity or deities."
"Divine magic, as the name suggests, is the power of their god or gods..."
"A deity (or deities) doesn't grant this power to everyone who seeks it..."
"...the ability to cast spells relies on devotion and an intuitive sense of their deity or deities wishes."
"...wade into melee with the power of their deity or deities on their side."
"...carrying out god or god's will..."
It's just not practical, and grammatical issues with the mix of singular and plural.
They no longer publish a book like Deities & Demigods because it's somewhat useless on its own. First because the deities don't need stats like monsters. Second, because they really should be tied to the setting and the cleric class much more closely. Because a polytheistic world of some sort is the default, naturally the examples use a polytheistic approach. But there's nothing that's saying you have to run it that way.