D&D4 Wiki
Aegis of Shielding
Swordmage Feature

Target: One creature in burst

Effect: You mark the target. The target remains marked until you use this power against another target. If you mark other creatures using other powers, the target is still marked. A creature can be subject to only one mark at a time. A new mark supersedes a mark that was already in place.
     If your marked target makes an attack that doesn't include you as a target, it takes a −2 penalty to attack rolls. If that attack hits and the marked target is within 10 squares of you, you can use an immediate interrupt to reduce the damage dealt by that attack to any one creature by an amount equal to 5 + your Constitution modifier.

At 11th level, reduce the damage dealt by 10 + your Constitution modifier. At 21st level, reduce the damage dealt by 15 + your Constitution modifier.[FRPG:26]

Aegis of shielding is an at-will power available to swordmages with the Swordmage Aegis class feature. A swordmage selects either aegis of assault, aegis of ensnarement, or aegis of shielding as the benefit for Swordmage Aegis.