[thejeff]

10) My understanding is that they reduce dominion towards 0. Your dominion or an enemy's.

11) If the caster is scripted to cast a particular spell and can't find a valid target, they will cast another spell. If they can't find a target for any spell, like a low level priest with everyone blessed and no undead in range, they'll default to "Stay behind troops"
Post ninja edit: I normally wouldn't argue with lch, but I'm pretty sure about this. In practice this only shows up with H1 priests or with mages in the very early game when little is researched.

12) I believe domes work against anything targeting the province.
Including your own spells. Teleports, site searches, etc.

14) Twist fate works against (most?) magical attacks. Magic Duel may be an exception, there may be others.

15) Bodyguards are ignored for troops to stay behind.
Post ninja edit: I'll have to check this.