I read novels and found a sentence or a phase after the sentence with a comma. I would like to know how it works.
The blade left a trail of golden light as it slashed down, ripping apart the enormous brown boulder that had just been lobbed at him. [The word "ripping apart" was described that it happened at the same time as what happened in the first sentence?]
Tens of thousands of figures could be seen battling on this plateau, swords clashing against spears, explosions of light and magic searing the air and sky. [How can we use v.ing without v. to be here? What does it call?]