I'm not sure you're right here. Suppose you could have a small suite of barbarian backgrounds, but then...how many can you think of that make sense for adventurers? Our standard Barbarian Warrior, maybe Shaman/Witchdoctor,...then what? Barbarian Chief? What other barbarian types could/would be adventurers? Barbarian Merchant?...how is he different from regular merchant dude? Barbarian Peasant?....still a Commoner IMO. If you really want to play one of these preliterate outliers, then the game is better off letting you kitbash a custom background rather than put all the possibilities in the game for everyone else to ignore.
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I am not sure if you're now thinking I was suggesting multiple barbarian backgrounds, but I wasn't... I was suggesting NO barbarian backgrounds at all, and instead to consider a barbarian human subrace.
So then you can have barbarian+clerics (shamans), barbarian+fighters, barbarian+rogues, barbarian+sorcerers etc. by combining it with classes and you can also have barbarian+merchants or barbarian+commoners by combining it with backgrounds.
Of course the limit of this idea is, as I mentioned already, that you cannot combine it anymore with races... you're stuck with human barbarians, and this can be wrong for many gaming groups. But notice that in 3e you had subraces such as Wild Elves for example, which were a little bit like barbarian elves.
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A human subrace? In addition to bordering on offending people sensitive to racial slights, intended or not, the big problem I have with that is putting a Maori inspired peoples and a Norse inspired peoples in the same subrace and just calling it good.
Remember what I said about making mistakes as a designer in assuming that everyone that wants to play your fantasy game also wants to play in your setting? It sounds to me in this discussion that you are increasingly not designing for a fantasy game which would suit everyone who has been playing D&D over the last 30 years, but which suits your particular setting specificly.
On the contrary, I am
trying to understand what is the common ground of traditional D&D gaming groups. Might be wrong, but IMHO when someone says "Barbarian" in a game of D&D, the first thing that comes to mind to most players is in fact Conan the Barbarian, or alternatively the barbarian invasions of the dark ages.
So I am trying to think: what are the traits that more-or-less define the most common archetype of a D&D "barbarian"?
My answer is: physical toughness, survival instinct, familiarity with the wilderness. All these may be connected with the concept of less-than-civilized tribes, on the ground that having a more primitive civilization (perhaps even being nomadic) generally forces all their people to be tougher against the hazards of the wilderness and travel.
There is another trait which defines a typical D&D Barbarian, and that is the chaotic rage, but IMHO there are quite a lot of people who have expressed their preference for rage to be separate, so that non-barbarians can have it too and not all barbarians need to be berserker by default, thus I'm leaving it out at least for the moment.
Then I think about what are the current mechanics at our disposal: class and background first. Can I use these to represent barbarians well?
I bet that 5e ultimately will have a Barbarian class, it worked well enough in the past. But if I like the idea of a barbarian
tribe, clearly they can't all be barbarian-classed (at least not all single class). They can't all be barbarian
warriors. It's ok in 3e, you use the Barbarian class for barbarian warriors, then you can use the Cleric class for their Shamans etc. I would prefer however that you could make a barbarian Fighter, a barbarian Cleri, a barbarian Sorcerer, by combining "barbarian" (whatever mechanic it is) with classes.
Background, I am against it. Because the mechanics of background are granting 4 skills and a Trait. Maybe if you can design a GREAT trait for a barbarian background, it would be OK. But it's the skills that leave me skeptic, because beside Survival I don't see everyone in a barbarian tribe being all good at the same skills. They are a tribe, a community, so IMO they will have people specialized at different skills. They will have their commoners, their merchants, their soldiers, their sages, etc. so it might be best if "barbarian" isn't a background so that it doesn't "lock" the choice of a background.
Thus I suggested using a subrace, why? For two reasons:
- races and subraces are the least strictly defined "character building mechanics"; we have subraces granting larger HD, weapon dice increase, ability bonuses, skills, perception improvements, and totally unique features; there is A LOT of freedom here, so we can come up with ANY defining features that is reasonably good for ALL barbarians (at least the most archetypal ones) including Norse and Maori if you want, without being stuck with 4 skills and a trait (although the trait IS free from design constraints! but it's quite too little)
- using a subrace still leaves each PC the choice of class, background and specialty to make plenty of different "barbarian" PC in the same tribe or world