No matter how many times its explained to him Jim never talks about Conjuration and Necromancy as being the same school of magic. When he says Felix Caelus is the expert when it comes to Conjuration, he's speaking to lesser daedra--to familiars and atronachs who protect the mage when called upon. To the Princes Felix holds reputation with and barters for favor. But he knows logically that in Tamriel they are very much one and the same. Perhaps it's why he'd assumed those undead would yet still be roaming around in the depths.

"You were afraid." Jim can't blame his husband for that. He's afraid right now just thinking about what's still down there. What they're going to have to go back and face. "Did...did you flame atronach do this to you?"