Magic Absorbing will negate a portion of all magical projectile attacks. The maximum amount of damage negated depends on the item and is based on the base magic defense of the character wielding the item. Maximum damage reduction is achieved at base 319 Magic Defense (Skill).

Equipment Max Reduction
Aegis of the Gold Gear 25%
Aegis of the Golden Flame 10%
Fetish of the Dark Idols 25%
Gear Shield 10%
Raven Aegis 25%
Sanguinary Aegis 25%
Shield of Isin Dule 10%
Shield of Perfect Light 10%
Tome of Caustics 10%
Tome of Chill 10%
Tome of Flame 10%