The 1874 RLDS edition accidentally added the preposition by before the relative clause “which he hath devised to ensnare the hearts of men”. The typesetter was probably influenced by the preceding by in “which comes by the cunning plans”. The 1908 RLDS edition restored the correct reading that lacks the by at the head of the second relative clause.
Summary: Maintain the current text in Alma 28:13 without the preposition by before the relative clause “which he hath devised to ensnare the hearts of men”.