A world where, instead of aging in years, the people age in knowledge. So, instead of dying once a general age was reached, they die once they achieve a certain amount of knowledge. A man could live forever if he never learned anything, or could die after reading a few choice books. Of course, the knowledge of the land would be regulated, like medical drugs.
Urbants-Creatures that move quickly around on their massive arms, and their "legs" dangle about from their torso, at about elbow length. They can move fairly quickly, but not as fast as an obese human, and can "jump" fairly high. Their "legs" are very powerful, and can kill with one blow. The bad thing is, Urbants cannot block attacks at their heads, which have relatively no neck, from the length of their legs being so short.