An Assault Rider is a centaur-like creature with a black, equine lower body with red hooves. Its upper body is muscular, vaguely humanoid, and has black skin. It wears grey Chinese armor over most of its body, as well as a small, conical, silver helmet with two curved, golden feathers and a red cape. Its pitch-black face is almost entirely obscured by its helmet, though its glowing, yellow eyes are visible. It carries a long guan dao with an angular, gold blade, a silver handle, and a red horsehair tassel at the base of the blade.
In Kingdom Hearts II Final Mix, the Assault Rider's body becomes predominantly lilac-colored, and its hooves become gold, and its hands and tail become violet. Its armor becomes red-violet and orange with gold lining. Its helmet, though still silver, is a bit brighter, its cape turns yellow, and its face becomes violet. The Assault Rider's guan dao now has a silver blade and an orange and purple handle, though the tassel remains red.
The Assault Rider's name refers to its battle prowess, as "assault" means "to attack", and its equine lower body, hence "rider".
Getting close in can really take a chunk out of Sora and friends' HP, and can also take a large chunk out of your morale gauge during missions, so long-range magic is less dangerous. Although they have powerful attacks, they won't attack unless they are in range at the beginning of the battle or are provoked. These Heartless get especially fast when their HP gets low.
When fighting an Assault Rider during the first visit to the Land of Dragons, keep a distance and pelt it with magic, preferably Thunder or Blizzard. An alternative is to simply go to town with Valor Form, hammering the Assault Rider with as many combos as you can before the Form Gauge runs out. Guarding often is advised.
During the second visit, use Master Form along with Wishing Lamp and Follow the Wind, attacking with combos and powerful magic such as Thundara/Thundaga and Blizzara/Blizzaga. When it starts getting more aggressive with its attacks, don't hesitate to use Reflect magic when necessary.