The mere presence of a powerful paladin can instill great courage and inner strength in those around them. This powerful, spiritual surge actually increases the defensive capabilities of those gathered near the paladin[1]
Patch 9.0.1 (2020-10-13): Redesigned as a level 28 ability for all paladins (was a level 60 Holy talent). Party and raid members within 40 yards are bolstered by their devotion, reducing damage taken by 3%.
Old: Allies within 10 yards take 20% reduced damage, split over the number of allies in the aura. While Aura Mastery is active, all affected allies gain the full damage reduction.
Hotfix (2016-09-21):Devotion Aura should correctly be canceled upon changing specializations or talents
Hotfix (2016-09-16):Devotion Aura should no longer drop off of the Paladin using it if the Paladin moves too quickly.
Patch 7.0.3 (2016-07-19): Redesigned as a level 60 Holy paladin talent (was learned by all paladins at level 60). Allies within 10 yards take 20% reduced damage, split over the number of allies in the aura. While Aura Mastery is active, all affected allies gain the full damage reduction.
Previous: Inspire all party and raid members within 40 yards, granting them immunity to Silence and Interrupt effects and reducing all damage taken by 20%. Lasts 6 sec.
Patch 6.2.0 (2015-06-23): Now reduces all damage taken, not just magical damage.
Patch 6.0.2 (2014-10-14): Now only available to Holy paladins.
Patch 5.3.0 (2013-05-21): Now clears all silence effects when used.
Patch 5.0.4 (2012-08-28): Redesigned as a level 60 ability (was level 5). Inspire all party and raid members within 40 yards, granting them immunity to Silence and Interrupt effects and reducing all magic damage taken by 20%. Lasts 6 sec.
Old: Gives additional armor to party and raid members within 40 yards. Players may only have one Aura on them per Paladin at any one time.
Patch 4.0.1 (2010-10-12): Spell ranks removed. Now learned at level 5 (was 1).
Patch 3.3.0 (2009-12-08): When in a party with another paladin using a different rank of this ability, it is no longer possible to see two different Devotion Aura icons displayed as buffs.
Patch 3.0.8 (2009-01-20): When mixing two different ranks of this ability in a party, players will no longer sometimes see a spurious second copy of the buff.
Patch 0.7 (2004-06-15): More frequent ranks added.
[Aura Mastery], 
[Merciful Auras]
[Auras of the Resolute] class talent.
Patch 10.0.0 (2022-10-25): Now granted by the class talent 
