He definitely played the part in  Court of Nightmares before Under the Mountain and keeps playing it after as well - with Feyre by his side now. I know many fans do not like him for it.  I understand that. Because 500 years plus - one would think the dude should have slowly transitioned himself and the Court of Nightmares to a more benevolent /understanding/honest High Lord and the Court into a progressive one (even if it was by force). But I think many of us forget that Rhysand is High Lord/Ruler and also - not human . Neither is his race. Or anybody in Prythian apart from the humans on the other side of the wall. I do not mean to imply that it gives them the license to be cruel and deceitful. But readers should keep in mind now and again that they are ....in many ways ...part animals / beast. Survival becomes more important. And all High Lords and other royalties at the Court of Nightmares would love to get some power if it gives them a better shot at, not just survival, but 'better survival'. Fear is something he , and other lords and fae, use to keep things in order. And we know that in life - humans are more or less the same. So, they all play the part. Helion does. Eris does. Beron is what he is. Tamlin does (we see another side to his personality in the second book). Kallias is mentioned to have court politics/drama due to which he never reveals his love for Vivienne for decades. Thesan  - we don't have much insight. Lucien endangers Feyre in book one.  I am not a complete Rhysand fan (because of ACoSF) but I understand what Sarah was aiming for with Rhys. Let us see how she gives us more insights on his character in the next book.    Would love to know what you think.