What if some crazy wizard created an artifact that empowered rodents that touched it with one random supernatural power? Preferly right out of the pages of your favorite four-color. (But only one power!) This item does not convey any sort of intelligence boost.
Somewhere along the line, someone very powerful lost their marbles. Literally. Possessing a marble allows incredible clarity of thought about a particular related subject.
To become a warrior in a tribe. -no food, drink, or sleep for 4 days and nights. -change into special clothes and painted enter hut -slices of skin carved from their chest and shoulders -wooden skewers through the bleeding flesh behind the chest muscles -stout thongs, secured to rafters were tied to skewers -hoisted from floor by these and weights were attached to their feet -twirled around till fell unconscious -when recovered from this, given a hatchet to cut off their little finger -ropes then tied to wrists and force to run in circle like a horse until he passed out -if survive all this he can return to his family in honor knowing he is now a warrior.