The sentences after comma, how to use it for describing anything?

Question

I read novels and found a sentence or a phase after the sentence with a comma. I would like to know how it works.

1. 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?]

2. 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?]

Answer 1

This is called an appositive phrase, which is an incomplete sentence that uses the gerund tense added in between commas.

It serves to describe what came before it, in terms of subject and action.

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