Yesterday I posted about how there are a lot more orc wizards in DF Felltower than in one of the games that influenced it heavily - AD&D.
It leads to a larger question - how many wizards?
If wizardly magic is common enough that:
- orc have wizards and send them on patrols;
- almost every race that can have wizards has wizards;
- some that can't really have them have them anyway;
- PC wizards exist in whatever number they make them up;
- PC wizards are largely exceptional by being a) PCs and b) 250 points;
- NPC wizards have cushy jobs in town like "enchanter" or "alchemist" or "Power Item recharger";
- wizardly spells have affected the world around you (anti-magic paint coatings on walls, vast dungeons shaped out of the earth with a trivial earth spell, magical traps, summoned monsters, owlbears);
then . . . how many wizards is that?
The short answer is: as many as we need.
The longer answer is: as many as we need to do all of that, but not make wizardry so common it overwhelms the fun of being one or having it.
Also, the answer is: I don't know, I can't and won't calculate the answer.
It's really a pretty simple thing - we're playing Dungeon Fantasy, not Demographic Fantasy. So I really don't care how many wizards there are. In a larger game, it's worth figuring out ballpark numbers. It's worth knowing that the PCs are x% of the world's number of wizards, or that given 1,000,000 people in this fictional kingdom there should be Y wizards.
But in a DF game?
A game where going into dungeons for loot is the centerpiece activity of the game?
It only matters how many wizards are in this area. How many these orcs have. It doesn't matter if dwarven wizards are rare if I need three of them for this encounter area - then there are three here, no matter how many are elsewhere. The answer always back-fills the world, not the other way around. If someone makes up a wizard and says, "I'm from a big family full of wizards in a country full of wizards" then there are lots of wizards in that family and in that country. If someone says, "I learned this spell in Necromancy Club in primary school!" then there are primary schools with clubs that specialize in Necromancy. If I put dozens of wizards in a group of orcs or goblins or elves, then it's plausible other groups have dozens, too. If I put one, it could mean the others have one or the others have more - depends on what I need.
It's, again, backstory filled in from play. And it's worldbuilding from actual play outward. I highly recommend it for a GURPS Dungeon Fantasy game - or indeed, any other system you're using for beer-and-pretzels gaming.