Summary: 

Smallish bipedal creatures that are only about the size of a 10-year-old human. They have hooves instead of feet, the lower part of their bodies being very goat-like, while the upper part of their body looks more human-like, safe for their scaly skin that also covers their slightly more reptilian face. While the majority only has two small horns,  some will grow 4 horns. Some have small tails like goats, while others have tails like ones of a lizard.  Some also possess bird wings on top of all their other characteristics 

Reproduction:

Imps are very fertile and have a libido almost and strong to the one of a succubus, the females having up to 3 babies per pregnancy. The female has multiple eggs per cycle and can have children from multiple different males at the same time. Statistics show that the average male would father about 17.7 children in his lifetime, and the average female would birth about 12.4,  but these numbers have been greatly reduced by the ease of access to contraceptive methods and rise of monogamy over the years, partly caused by the rise in the female population. As this is being written, the average male will father 4.6 children,  and the average female will birth 3.7 children.

Biology/life cycle 

Most imps are born able to see and can walk only a few hours after taking their first breath. They'll be about the size of a rat when they're born but will reach adult size in around five years. They're naturally fast learners and will know how to do advanced maths by the age of 3, partly because they're already ready to learn by the age of 8 months.  

They're very resistant, their bones being very flexible and resistant to breaks, they also replace lost blood and coagulate a wound shut in less than a minute, their skulls are nearly impossible to break. Even a jumping elephant would have trouble cracking them. This makes them really hard to kill, and so it's rare for one to not die of old age, at the age of 45 to 47 (as this is being written). 

Additional facts:

Imps are often associated with mischievous creatures, they are known to be insidious and intelligent. This association may have been born as a consequence of the “Imp plague”, a war that also originated the expression “Imploberé”. Imploberé is a form of warfare where one does not physically harm their enemy, but rather strains their resources by either stealing them, making them waste said resources, or cutting supply and trade routes to the enemy's land, until the enemy gives up.

The imps in Krotinialer use these tactics in the human population after the king decided to pay 20 coins per imp head. The bounty was lifted after five months of imps stealing all the food, money, and weapons in the kingdom. And the imps were even given control of the underground of the kingdom, hallowing it and turning it into a kingdom that ran 100 kilometers deep, which to this day is still considered a marvel of architecture, and the only imp kingdom. 

Personal experience:

I went to their kingdom once. It definitely deserved to be called a wonder of architecture, and even though it’s as advanced as the majority of other kingdoms, it still preserved its original… How should I put it… Messy but still organized and grand aesthetic, with rustic and urban structures blending perfectly and harmoniously. The imps I talked to were really helpful, and all gave me a lot of info about the city, their culture, biology, etc. They seemed all really excited to have a nice “not-imp” in the city.