The Aegis of Ages

This shield was carried by the nigh-invincible cleric Angeron. Many often heard Angeron boast that the same style of attack could never hurt him twice. Forged by forces long since forgotten, the Aegis of Ages is timeless and unbreakable.
Whenever an attacker hits you with a melee or ranged attack, roll a d6. On a roll of 4-6, you have resistance to slashing, piercing, and bludgeoning damage until your next turn (this damage reduction includes the attack that hit you).