Technically mummy fear isn't a spell, supernatural ability though it is. So It wouldn't be subject to the +2 dwarven anti-spell bonus. For mummies, dragons, skalds etc, this fear effect is more aura-based than from any spell being cast. SO while a dwarf would get the +2 vs fear spells, he wouldn't get it from fear effects. And these fear effects would be able to persist in anti-magic zones like the rift.
To protect yourself from supernatural fear, increasing the will save directly should work well, I think Diamonds?. Mind affecting spell gear like garnet rings wouldn't work however, since even though the fear supernatural ability seems like a mind affect, it isnt specifically a mind affecting "spell". Skabot found that out the hard way in the arena when he tried to use mind blank against the fear and immunity: necromancy from Shadow Shield against Farros, and ran screaming until he was ruptured by death wails.
Fear is one of those nasty things that mind blank just wont shrug off.
Other ways to combat fear are via things that specifically combat fear itself, explicitly defined as fear and not spells or mind affects. So standing next to a Paladin should give you a +4 vs fear, being a paladin makes you completely immune without needing any will check. The Noisemaker Helm is another very useful anti-fear item in game, with +4 vs fear. A 1st Level Cleric spell "Remove Fear" will remove any fear effects if already suffering them, and provide a further +4 against fear for the duration of the spell... I usually almost always use it as a pre-mummy buff in Storans. So, with remove fear, a paladin buddy and Noisemaker's helm, you could theoretically stack up to +12 vs fear. I'm pretty sure it stacks, though Haven't tested it for certain though. Also, bring a bard! Bardsong is excellent against any will save based attack.
Other things that would seem like mind effects but really aren't treated as such include Phantasmal Killer and the bigger area effect one. Those are technically illusions, despite the will saves invovled, and only True Seeing seems to work as a shield, not mind blank or bonuses vs. mind effects. Some Will Save based gaze attacks that kill directly that or thwarted by will saves are technically curse effects, and a mind blank or save vs mind effects will not protect anyone from curses. The snake's gaze can be mindblanked however, that's considered more of a mind effecting hypnotic gaze than a spell or curse, and it can persist in anti-magic zones. Things like bane and storms of vengeance, dirge and the like are also likely not considered mind effects, though they use the will save usually.
Also, while listening to a speech by FDR can provide a morale bonus vs. things that cause fear, it is wholly ineffective against the fearful effects of fear itself.
