He used Genjutsu: Sharingan against Ay, the only other MS user to use that is Sasuke, who has amateresu on one eye and enton on the other. But since Enton is basically manipulating the black flames, then does that mean the enton eye is useless without the eye that casts the amateresu? As in, if that eye got sealed? What would the other eye do since there are no flames to manipulate? You're probably wondering what I'm tryna get at yeah. Well, remember that Madara used Izanagi to trick Hashirama, which means that that particular eye got sealed away and therefore should not have it's MS justu anymore. What if that eye was the one that casts amateresu. Remember also Tobirama comparing Sasuke's blaze release to the time he saw it before, maybe that was Madara's blaze release he was talking about? Oh wait.....aaargh forget I said anything, coz that still doesn't explain why we never saw Madara use Amateresu/Blaze Release in his many fights with Hashirama.