Arcane Shield (Feat)

You can convert any spell into a defense.

Prerequisites: Arcane Caster Level 11

Related: Arcane Insight (Feat)

Benefit: As an immediate action, you can sacrifice a prepared spell or unused spell slot of 2nd level or higher and gain a shield bonus to AC equal to 1/2 the level of the spell or spell slot you sacrificed for 1 round (drop fractions). 0th and 1st levels spells cannot be used to trigger this effect. This shield bonus lasts until the start of your next turn.

Note: This feat lets you use your immediate action at any point prior to damage resolution to attempt to retroactively make a successful attack miss. Obviously, you can also use it before an attack roll.