悍ましき罠should beおぞましい罠in modern Japanese. The author used the classical Japanese ending -ki for adjectives, most likely to give it an air of sophistication and sense of poetry. (e.g., 愛しき人 is a poetic way to say 愛しい人） The phrase means "detestable/abominable trap/snare." Technically, with the kanji 堕, it should be 堕される（だされる）but I am guessing that the writer used 堕 as a synonym for 落とされる, since 落、堕、墜 all mean "to fall" in Japanese. The verb is in the passive form, and it means "to be dropped." To me, the use of the kanji 堕 gives the word a sense of "moral decay" (as in fallen into moral decay).