Ball sprite
From Warhammer 40k - Lexicanum
Ball sprites, also known as fire dogs[1a] and death sprites[1b], are dangerous carnivorous ball lightning-like creatures native to Chevreuse. They are fast-moving balls of light, and they are impervious to gunfire. Even bolter fire will pass through the body of the sprite without exploding or causing any significant harm. The scorching bite of a fire dog will kill a normal unarmored human quickly.[1a]
