Who revived Gaara?

Deidera of the Akatsuki killed him when he extracted the Shukaku demon from him, though Chiyo (the Sand kunoichi who sealed the demon in him originally) sacrifices her life by trading her life for his. He lives on and protects the leaf ninja as well as his brother, Kankuro, and sister, Temari. He does retain his ability to manipulate sand, though his powers are severely diminished, but they will return as true strength is found by protecting loved ones and family.