Whenever Bruna, Light of Alabaster attacks or blocks, you may attach to it any number of Auras on the battlefield and you may put onto the battlefield attached to it any number of Aura cards that could enchant it from your graveyard and/or hand.
5/1/2012 Only Auras that could legally enchant Bruna may be attached to it, whether they’re being moved from other permanents or being put onto the battlefield. An Aura with “enchant land,” for example, could not be attached to Bruna this way.
5/1/2012 All of these Auras will become attached to Bruna before combat damage is dealt. If Bruna is attacking, these Auras become attached before blockers are declared.