Though Scar was superior to Kieran in every aspect imaginable — speed, power, technique, experience, battle sense — the Old Myths and their Successors couldn't look away from the spar between mentor and pupil.
Such a lopsided fight should have been mind-numbingly dull to watch, even more so because it was a spar and not a life-or-death battle where no holds barred applied — everything at your disposal could be utilized to ensure survival.
At some point, Altair had stopped leaning against the pillar for support and stood upright, his eyes trained on the rapid exchanges. It wasn't their movements that caught his attention, but what Kieran was doing in response to his mentor's counters and sometimes monstrous blows.
He was adjusting his use of his Innate Ability in real time to rebuff his mentor.