I could totally see this being the main theme of an old-school RPG - the instrumentation is quite fitting for that kind of sound I think.
While I do like the melody quite a bit, as well as your choice of harmony, I think the fact that the trumpet is playing nonstop for almost the entire duration of the melody feels a little unnatural to me. IMO the melody could've made good use out of little (no longer than a quarter note) breaks or pauses at the end of phrases.
Thanks for sharing, and keep up the good work!