2) internal rhyme
Internal rhyme refers to a sound device in poetry, where a word in the middle of a line rhymes with a word at the end of a line, or rhymes with a word in the middle of the next line.
In this instance, "peering" occurs in the middle of the line "Deep into that darkness peering, long I stood wondering, fearing", and it rhymes with the word "fearing" at the end of the line- representing an internal rhyme.