Additionally, if you are using the
LeFemm Armor official plugin, Sirollus will be wearing a complete set of Gold Armor - which looks somewhat odd on him, as the armor was designed to be worn only by female characters. This is one of only three sets of this armor available in the game. (It's possible the developers gave him the armor intending him to have it for sale, without taking into account the fact that he would automatically put it on instead.) This will make getting it off of him without killing him somewhat difficult. You'll need to use
Disintegrate Armor spells until it breaks, then cast
Calm to stop him from attacking you, and then pickpocket it from him. Alternatively, you could sell him better armor, which he would put on in its place. Unfortunately, only very rare Ebony or even rarer Daedric Armor will be good enough to convince him to give up his Gold Armor willingly.