[thejeff]

Yes, you have it exactly right.
All I meant by 'random' is that which order (high-to-low or low-to-high) it goes in is chosen randomly. Or pseudo randomly, if you want to be precise.
Obviously not encryption algorithm worthy, but I think it's a clever trick. It really covers about 95% of what you'd get out of completely randomizing action order, at a much lower cost. There are a handful of edge cases where you can abuse it, like using high and low id casters, but mostly all that's important is that you don't know who's going first. Not doing more work than you have to is elegant.

However, I think you may be confused, Pyrrhic. It uses unit ID, which as far as I know isn't displayed, not Monster Number, which I think is what you're referring to. Units are displayed in the main window or the Army Orders screen in ID order. That's the only way I know to determine relative order. Monster Number is shown with .
So if you use casters at the top and bottom of your screen, you'll most likely hit him with some of them. Of course, you have to use twice as many casters and gems, so it's not always worth it.