thank you! Why span for battle and not turn?
Span: Battle means the event will trigger once per battle, which seems like what you're most likely going for. Span: Turn means it will trigger every single turn. If the boss's HP can rise above the limit and go back to the original battle theme, then perhaps "Turn" is what you want, but I would recommend "Battle" in the general case. ("Moment" should certainly not be used for this, at least not without some tweaks.)