Berserk is Saïx's Limit Break. It causes Saïx to enter a state of berserk and his claymore to change form. Pressing will make Saïx leap at targets with an aerial shockwave, while not pressing anything causes Saïx to rush in a single direction, leaving shockwaves in his wake. During the Final Limit, the rate and range of Saïx's attacks are increased, and pressing will cause Saïx to jump into the air and release an area burst shockwave, inflicting massive damage to nearby targets.
Kingdom Hearts 358/2 Days