A special ceremony called The Ceremony of the Keys is performed there nightly. What is the adverb, then what is the word that modifies it and is that word a verb, an adjective or another adverb?

There are two adverbs in that sentence.

Both "there" and "nightly" modify the verb "is performed."

To identify the adverb in the sentence "A special ceremony called The Ceremony of the Keys is performed there nightly," we need to focus on words that modify verbs, adjectives, or other adverbs.

In this sentence, the adverb is "nightly." It modifies the verb "performed." The word "nightly" describes the frequency or manner in which the ceremony is performed, indicating that it happens every night.

In conclusion, the adverb is "nightly," and it modifies the verb "performed."