
I think the 'El' that the unicorn was reffering to is Elwien, you know how he said 'El' was the first human to summon Elqueeness, however our El clearly knows that Isana is the first human and he could feel it. What if 'El' wasn't a human, but the Elqueeness himself? He could have gotten someone else to disguise as Elqueeness and pretended to be 'El' himself.
;)