SFS Standard Nimbus Block Feat 6

Source Player Core pg. 146
Prerequisites Nimbus Ward, or Solar Shield
You've combined the strength of your defensive powers such that your solar nimbus bolsters your solar shield. When you Shield Block a melee attack with your solar shield, as long as either you or your shield take damage from the attack, you can use Nimbus Ward as a free action.

Traits

Attuned:You can't use abilities with the attuned trait while you're unattuned. Many attuned abilities require you to be specifically graviton-attuned or photon-attuned, while others can grant additional benefits based on your current stellar attunement.
Manifestation:Feats with this trait enhance or alter your solar manifestations (flare, nimbus, and weapon) or allow you to create a new type of solar manifestation.