Hi and welcome to the forums! Let's get into this video.
First of all, what do you mean by semi-improvised? Is there a draft score that you could share?
It sounds nice, not really like a fantasy (to me, of course) but more like some epic intro/medley of a medieval series or film. The 123-123-12 rhythm seems to be one of the main features of this idea, as well as the right-hand octaves boosting the melody and the limited harmony (which is not necessarily bad at all. It all depends on what you want I suppose). I believe that this is a good start to produce something quite cool, but not the finished product (and that would make sense since you said it's a semi-improvisation, right?), right now it feels to me like a bunch of more or less decent (some of them quite cool like 1:26 to 1:38 approx) ideas that lack a defined structure (which again may be what you want) and that in sum give me a feeling of listening to something a bit generic.
You seem to take some more risks with the rhythm (and perhaps with harmony a little but not really sure) around 4:30 and towards the end. Those risks perhaps could have been taken before and thus added some more variety to the piece. Still, parts like the one I mentioned (1:26-1:38) do this job more or less good.
I still have to check your next "iterations"... Just to clarify, lol, they are created by you, right? This is likely a dumb question but those titles suggest me something AI-related.
Kind regards,
Daniel–Ømicrón.