Okay, Cha0s and I were arguing about this tonight, and I think i'm right...
The new Catelyn says you can put her into play knelt as a defender. From my understanding of how timing works, this could be done after Stealth is declared during your effects window after defenders are declared, meaning I can drop Catelyn into play after my opponent has had their chance to Stealth something. This seems to make sense to me, because you could add Greatjon Umber to the challenge after defenders are declared during your effects window if necessary, and both of their abilities are "Challenges" abilities so they would work off the same timing. Am I wrong?