Sanctity Aura

Sanctity Aura is a talent in the Retribution tree; you will need to spend 21 points in Retribution to learn it. It is a staple of the Retribution specialization due to the offensive, DPS nature of the spec. Its presence typically indicates that the paladin is primarily oriented towards dealing damage and enhancing his party's as well, becoming something of a "combat buffer". This is now removed from the game.

Talent improvement
Improved Sanctity Aura increases damage of anyone affected by the aura by 1%/2%. This includes physical as well as Holy damage. This is a base change to melee damage and an end-damage amplification to spells. (Note: Prior to Patch 2.1.0 this instead gave a 3%/6% bonus to healing done to party members.)

Tips and tactics
Sanctity Aura is, for obvious reasons, the ret-spec aura and part of what separates ret pallies from the other specs. With the Improved Sanctity Aura talent, it benefits all other damage-dealing classes as well.

Sanctity Aura is very useful for shockadins (40/0/21 build), because it increases their Holy Shock and Seal of Righteousness damage by 10%. Smite Priests love this aura because it provides a flat 10% increase to their DPS.

Paladin tanks also like Sanctity Aura in their group, as it helps their threat generation enormously.