You make a better use of magic items.

Prerequisites: Priest or Magician or Blackmage or Sorcerer.

Benefit: You may leave a spell slot unprepared to gain a bonus on saves or armor class as a immediate action until the start of your next turn. To do so you need a magic item providing a resistance or deflection bonus and you need to leave slots unprepared to use it. The magic item has to be as highly enchanted as the bonus you want and the spell slots level must be equally high.