As I understand it, ‹asy› and ‹ìsy› denote prospective aspect, AKA going-to future. E.g:
It's not really a prospective marker
, though some uses of the prospective are covered by it. You cannot use it to say, po tasyaron
for all senses of he's going to hunt
, only when you have some intention about the situation. I don't think it would make much sense to use an s-future about a situation over which I had no control, but I can still say, "the Mississippi river is going to flood."
Frommer himself says he didn't use it as often as he could have, so I wouldn't be too alarmed by it not occurring in the film more. It does show up in some of the game dialog, apparently.