Learn French: Découragés par le scorpion, nous allions abandonner le camp. - Discouraged by the scorpion, we were going to abandon the camp.

In this sentence, découragés is a detached past participle acting as an adjective. Even though it is separated from the rest of the sentence by a comma, it describes the subject of the main clause, nous (we). Because nous is plural, the participle must agree and take an s. If the group of people were entirely female, it would be découragées.

What is the exact function of placing Découragés par le scorpion at the beginning of the sentence?

Placing a participle at the start of a sentence creates a detached phrase that implies a cause or a time. Here, it acts as a more elegant, concise shortcut for expressing a cause. Instead of spelling out the full reason—Parce que nous étions découragés par le scorpion... (Because we were discouraged by the scorpion...)—you simply start with the descriptive participle.

Why use the imperfect tense allions instead of the passé composé (sommes allés) here?

Nous allions abandonner is the past equivalent of the near future tense, translating directly to "we were going to abandon." You must use the imperfect (allions) because it describes an intention or a state of mind that was ongoing in the past. If you used the passé composé (nous sommes allés abandonner), it would mean you literally travelled somewhere in order to abandon the camp.

Could I use quitter instead of abandonner for "to leave the camp"?