Catch is in the infinitive form because it is before to. An infinitive is when the main form of the verb is preceded by the word to. Similar to a main verb, it expresses an action.
covered with ancient artwork - participle
A participle phrase begins with a verb and often can include other modifiers. A participle is used as an adjective in the sentence. In this sentence, "covered with ancient artwork" is used to describe the walls.
A gerund is a verb that is used as a noun in a sentence. A gerund often ends in -ing. For example, Swimming is my favorite sport. In this sentence no one is actually doing the action of swimming. Swimming is a thing/sport in this sentence.
He lieth in wait secretly as a lion in his den: he lieth in wait to catch the poor...
The verbal in this sentence is “to catch the poor” and it is an infinitive phrase that acts as an adverb of reason.
The walls, covered with ancient artwork, revealed much about the people’s culture.
The verbal in this sentence is “covered with ancient artwork” and it is a participle phrase that acts as an adjective that is modifying the noun “walls”.
Whenever repetition is used, it is used to bring attention to the main point, and to make it more memorable in the listener's minds. This makes you remember this phrase more, and makes you more likely to agree with it.
