Is the Prophet considered a magic being?

[llamabeast]

If you right-click on the Leadership statistic on a unit, it will tell you how many units of each type it's able to lead. You'll then find that your R'lyeh commanders can, in fact, lead huge numbers of magic beings.

[Herode]

If you want to see whether a unit is magical or not, check his statistics screen. The properties of the unit are listed above the magic paths (is he/she fire resistant, prophet, pretender, diseased, stealthy, etc. ?)
Magical units display a special icon (a kind of fey).

I don't know how you could make your prophet a magic unit if his chassis do not say 'I am a magic unit'. But if you empower him with whatever path, he will be able to lead a few magical units. Not sure it's worth the price, however...

[MaxWilson]

Crown of Command gives magic leadership, and you have Astral so you can forge it once you research Construction. It's not going to help you in the early game, though.

-Max