Hi! If I have to fight more than one enemy that attacks with craft and they have the same encounter number, do I have to fight them counting them as one as I do in battle with strenght? Thank you very much!

Hi everyone! I have two questions and I hope someone can answer me: 1) If 2 characters are fighting in the crown of command and one of them casts the psionic blast spell, does its effect last througout all the battle till one of them dies or does it last only for one turn? (as it says that it lasts for a battle) 2) Can I use any helmet or armour against the spell of command?