For every six feathers Kratos finds, he will be able to make a sacrifice to the gods and increase his magic meter, as well as fill it up if it is lacking. After 18 feathers, no more can be found in game.
Just as the Gorgon Eyes, only 3 Feathers are needed to increase the magic meter. Also the Feathers are no longer blue in color as previous installments, here they appear reddish orange.
The Feathers retain the reddish orange color from God of War III, but just as in Chains of Olympus 5 feathers are needed to increase the magic meter.
Glitch[]
In rare occasions in Ghost of Sparta, the last 5 Phoenix Feathers won't be saved in your profile the first time you finish the mission. Replaying the game and collecting the last 5 Phoenix Feathers will fix this problem.