Azazel
so this is about aazael, a two centimeter demon that has powers to do extraordinary things and george who calls him for fulfilling not his desires( cause azazel won't do it for him) but his friends or relatives. Azazel does exactly what george tells him but the consequence of that...well that is something you will figure out when you read it. won't rate it among the best of asimov's but definately a good collection of short stories to read !