Virtus Greater Shield

The virtus house is a house that has mainly battle magic. So, in the beginning of the house's conception they developed this spell that grants instant AC bonus and if the caster is protected, or if successful is shielding,  then the damage that was threatening the spell caster is reflected back onto the attacker. An invisible barrier of magical force appears and protects you. Until the start of your next turn, you have a +10 bonus to AC, including against the triggering attack, and you take no damage from magic missile.