You might end up rolling on the Special Allies chart based on your alignment and attract something really interesting like a black dragon or a sphinx! Or a stone giant!
Unlike followers, allies don’t actually work for you, as they are often way more powerful than your character. You can’t give them orders and expect them to obey. But they are interested in helping you. They are local personalities who’ve been watching your development, they approve, and they arrive interested in doing you a favor.