Old School RPGers may remember the badders as a race of mutant badgers from Gamma World. They featured in the classic Gamma World adventure Famine in Far-Go, and it is probably the illustration of the badder warrior training with a dummy that influenced me to include them in my Mutant Future campaign.
In my world, the badders are the ancestral enemies of the Coy Pu (mutant nutrias; if you don't know what a nutria is, they are basically 3-4' long rats that have taken over the Eugene-Springfield area of Oregon where I live). They spend most of their time in their extensive burrows underneath the swamps, and have hollowed out the southwest hills of post-apocalyptic Eugene where they raise their badder young and practice the art of warfare. The badders also worship the great worm Glargorion.
Glargorion is a unique mutation, a thousand foot long worm-like monstrosity that chews through solid earth and seeks out veins of metal to devour. After passing through Glargorion's digestive tracts, the metal is compressed, transformed and eventually defecated as pellets of glarg-ore. This metal is both incredibly strong and highly flexible, capable of stretching or compressing to twice or one half of its original dimensions, and it has many other interesting properties. It is capable of storing thoughts and images if a mutant with telepathic abilities spends time placing them in it. Images appear in perfect clarity on the side of the ore, while thoughts are accessible to any sentient creature that touches the metal.
When crafted by a master smith (and the badders have been perfecting the art of working with glarg-ore for hundreds of years) glarg-ore can be used to create weapons and armors that are nearly magical in their effectiveness. In game terms, when such an item is created a 1d4 roll equals the "magical" bonus of the item, +1 if the smith is a master craftsman. Glarg-ore armor is invaluable for mutants with the ability to alter their density, as it can expand and shrink with the mutant up to its natural limits (twice or 1/2 its size).
The badders have an intricate mythology centered around Glargorion, and spend a a great deal of time and energy collecting scrap metal from the ruins and dragging it down to a long tunnel far from the hub of badder society. There, the scrap metal is heaped up until it proves irresistible to the keen senses of Glargorion, and the mighty worm comes to collect its prize, leaving its valuable droppings in its wake. Glargorion visits only infrequently, and the badder shamans jealously guard the secrets of the pulsing rhythms that they send out into the earth with massive counter-weighted pillars, because these vibrations are the language of the god and help summon Glargorion when the precious supply of glarg-ore is running low.
Glargorion can be a cruel god, and its meanderings occasionally take it through the populated areas of the badder tunnels. Then pandemonium ensues as the 20' wide maw gapes and whole families disappear into the depths of the worm. Then the shamans seek for signs and portents to reveal what displeased the mighty worm god, and great sacrifices are offered in its honor. Despite these occasional terrifying episodes, the tremendous value of the glarg-ore and the reassuring knowledge that their god is tangibly real and swimming through the solid earth somewhere below serve to keep the worship of Glargorion alive among the badders.