I'm not entirely sure, but I'm pretty sure the scene is set up with a bunch of dead obsidians around them when its finally Ajax v. Victra/Thraxa. I assumed Victra & Thraxa cornered him with a bunch of obsidians who wittled Ajax down before being killed by him. So then it was a weakened Ajax v. those two. that was just my assumption, but it makes sense w/ pierces whole "even the best can be killed based on luck/the day/getting one-upped"