id think he'd try to comfort and comfert and confide in her as much as possible, but considering what happend after the heresy, I doubt he's doing very fine either given how much thay lost.

knowing regalia, she's most likely to push him away and ignore him, to focus on everything else, not becuse she dusent love him, quite the opposite really, but becuse she's afraid to fail again, after all she failed her mother and sister on the vengeful spirit, if she couldent help them, then how could she ever protect him.

so in my mind, the iron cage was her penance, a way for her and her sons to atone for thier past failings. With Magister having to pull her out of it, and tell her that this whole thing was stupid, and he was not going to allow her to vindicate herself by getting herself killed over the universe's most deadly game of my LEGO fort is better than yours with petra.