[magnate]

That's almost right - it actually starts at -4, ie. a +4 bonus to the MR save of the opponent. This is a "fear value" of +1, if you like. So +5 fear, from the Aegis or the Horror Helmet, will give a commander "Fear (+0)", meaning no bonus to the MR save of the opponent. Wearing both the Aegis *and* a Horror Helmet will give "Fear (+5)", meaning a -5 penalty to the MR save.

Some commanders (like Bune) have intrinsic Fear, and any Fear items will add arithmetically to that base value.

All death mages have Fear, where D1 is "Fear (-4)" and D9 is "Fear (+4)", and again any Fear items will add on top of that.

I don't know what happens if you Empower someone scary like Bune with death magic. Though I notice that Wraith Lords have greater fear than their death magic alone can provide, so maybe that just adds normally too.

CC