Terra dei Demoni

Well, it's not exactly a bug (and definitely not related to HD), although it's possible that the developers didn't intend it to work this way. To understand who Berserk affects and who it doesn't, you need to look at the highlighting of the hex and the highlighting of the stack when you hover over it – essentially, it works like a Fireball, but with a different effect.

I checked, hovered over Archons under Antimagic, and it works. Although, it's likely that it worked because they were expert units and also affected the Ballista. Or maybe it just doesn't care who it hits or not; it simply works on the entire area, regardless of whether there's anyone else there or not. But that's not the point; Berserk confused me, although without water, it wasn't very effective against Antimagic. And as the analysis showed, the opponent also had Chain Lightning, so there was no way to outsmart him.