Katashi is the current jinchūriki of of Shukaku — the One-Tail. The beast has a vast amount of chakra, even more so when compared to most humans. Shukaku's presence inside Katashi gave him the ability to to manipulate sand at will.
Half Shukaku Form
In some situations Katashi looses his cool and he slowly begons to slippe into his half Shukaku form. In this form the sand he carries slowly breaks down and begins to cover his body, covering his arms, and then his face. His face becomes distorted and it begins to look more like Shukaku's with yellow eyes and markings around the eyes, he even grows a tail from the sand which itself functions like a normal tail. In this form, his speed and strength increase. He can use the sand on his arms to stretch his limbs to extraordinary lengths. This form allows him to even fire off his limbs at will, but still have them remain under his control.
Miniature Shukaku Form
When he has no other options Katashi allowes the sand to cover his entire upper body, with only his feet remaining uncovered. While his facial features still remain slightly human, both his eyes resemble the Shukaku's. His body also has the same markings that Shukaku has on its body. In this form, Gaara is able to use the Sand Shuriken, and can also use Shukaku's Wind Release to perform Wind Release: Infinite Sand Cloud — Great Breakthrough. His speed, attack, and defence greatly rises while he is in this form. Much like Naruto's fox shaped chakra cloak, the sand is capable of absorbing a wide variety of attacks. However, the defence given to his body still has one weak spot. Since his lower half is not covered, the target could still perform an attack.
Full One-Tail Form
Katashi can use his sand to instantly create a giant copy of Shukaku with himself hidden inside. While in this form, Katashi transfers his eyesight to that of Shukaku's body in turn resulting in his own eyes losing their pupils. Unlike his smaller Shukaku forms, this form seems to not be able to reform itself if damaged.