If you think about even very common examples like, say, something that you would build, like a clock or a car or a group of people trying to accomplish something, it fails when its unity breaks down. So when it stops having a single form, which is functioning all together, then it sort of falls apart into discrete elements.

In fact Plotinus thought not only that soul in general is eternal so that you always have soul, but he thought that each person's soul is eternal.

The soul must be distinct from intellect because even at its best, what the soul does when it's thinking, is it thinks linguistically, it thinks in a temporarily extended way, so it for example, might go through the steps of an argument chain, as if you were going through a syllogism and seeing that something followed from the premises, whereas intellect simply grasps the forms.

The forms are part of the mind, or really are the mind, they're just the contents of this universal night.

In fact Plotinus does believe in divine providence, though when he talks about divine providence, he talks about that providence being exercised by the intellect and the soul of the world, rather than the One.

When you're seeking after bodily pleasure of food and drink for example, this is going to prevent you from doing what you should be doing which is contemplating.

Assuming there is an intellect, we're clearly not this universal intellect or we would know it. So that's one function of soul.