Devout Protector Expertise is a heroic-tier feat available to adventurers proficient with holy symbols. It was introduced in Dragon Magazine article Tools of Two Trades, for adventurers specializing in two weapon or implement groups.[Dr402]
This expertise feat gives a +1 feat bonus to weapon attack rolls made with any one-handed melee weapon, and to implement attack rolls made with holy symbols. The bonus increases to +2 at 11th level and +3 at 21st level.
In addition, while you use a shield, your allies gain a +1 shield bonus to AC.
Character optimization pages generally consider this a mandatory feat for characters using a shield, due to the global bonus to AC.