Orb of Light
An orb of light is a simple, white sphere of energy that glows yellow as it floats above the ground. After Master Xehanort corrupts the orbs of light summoned to battle Terra and Aqua during their Mark of Mastery exam with darkness, whisps of that darkness can be seen flowing from them. Even while tainted, the orbs of light retain their yellow radiance and white core.
Kingdom Hearts Birth by Sleep
Master Eraqus summons five orbs of light at the beginning of Terra and Aqua's Mark of Mastery exam for the Keyblade wielders to battle. Master Xehanort taints the glowing spheres with darkness, however, causing them to multiply and become more aggressive. When one of the corrupted orbs of light floats his way, Ventus destroys it and rushes to Terra and Aqua's aid. The trio manages to destroy every last orb of light, and Terra and Aqua's Mark of Mastery exam continues.
The Orb of Light is shown to be able to move around, attacking with several beams of light or by bouncing onto the player with similar movement to that of the Darkball.