What effect is created when writers form a compound sentence that begins with an incomplete clause?

An incomplete clause is also called a dependent clause. It is called as such because it is a part of the sentence that cannot stand alone. The advantage of using a dependent clause in the first part of the sentence is that, it makes the reader curious as to what happens next, or to what the writer actually has to say. In other words, it gives an anticipating thrill to the readers.