Some story-related stuff~
When Rot was raised as a death knight, the first thing that happened was him killing several of the cultists by tearing them to pieces, so they had to restrain him ‘till he calms down. While he wasn’t exactly what the lich wanted as the experiment wasn’t fully successful, he was very pleased with how bloodthirsty and completely crazy this one was, so…
Let’s say Bernard has his reasons for always trying to stay as calm as possible.