While preparing to enter Tailed Beast Mode, Gaara covers his body with sand. With this sand, he is able to form mouths all over his body. Gaara inhales with these and his regular mouth, causing his body to swell up. He then exhales this wind, mixing it with sand that's been coated with his chakra. The resulting sandstorm covers a wide area in front of Gaara and is very powerful, enough to knock down trees and deal extensive physical damage. For these reasons, it is a useful attack against multiple opponents.