So I first want to note that I don't want to start this post with the discussion of how the various editions of D&D change certain problematic elements. That will be later.
First I want to talk about an example mechanic in Neoclassical Geek Revival to set as a baseline. Much of the magic system in NGR is based around the competing claims of civilization and wilderness, with a potential third axis of destruction. Bringing order and security to the wild reduces the power of magic. Civilization would see demons and pagan spirits as one and the same, with different flavours to trick mortals. Pagans would see the demonic and the march of civilization as part and parcel, to build a mountain you need to dig a pit for materials. The demonic cultists would tell their flock that the unending darkness will soon envelope both of these petty factions as it subsumes the last points of light, best sell your soul while it confers a high price.
So religion is specifically never explained who actually is right, but it is set up to be a constant proactive conflict. If you have multiple faiths in the party, you'll risk getting into intra-party conflict. The trade off being you can let adventures write themselves if you don't.
This moves into magic-users, currently I have more remote areas giving more mana back. But I also note that Mystic Wastelands may cause mutations.
For the 2013 Printing I am going to be a little more explicit. I am currently using the numbers based on wilderness to show the odds something supernatural will occur based on how remote an area is. This works out remarkably well. Basically for each campaign (or region) you would write up a list of a few "natural magics" like "An unburied body may rise from the dead!" or "Burning a chicken egg in a church as it burns to the ground will cause it to hatch a wyvern". The amount of mana a region generates in a day is the % chance the event will happen.
This maps out to
0% chance in the city
<1% chance in the rural (so round down to 0%)
1% chance on the frontier
3% chance in the wilderness
5% in uncharted, virgin territory
24% chance in a mystic wasteland.
100% in a magical vortex
There are also of course going to be spots in any region which are one level more magical (haunted houses, ley lines, etc). So murdering someone in a haunted house has a slight chance of causing the body to rise back to unlife.
Once I remember being asked "why is it important to have a method to know the strength of a giant centipede?" and my answer then is as now: When you have a few numbers to work with you can work out repeatable subsystems that aren't purely arbitrary on the fly.
So the OSR is a tag some people use to self identify their work. It contains members of all genders. Whatever version of D&D you like is best.
1 hour ago