He loved enterprise, hardship, and even danger
There is no explanation for why Mary Shelley remakes Henry Clerval in so robust an athletic mode, replacing the dreamy, poetical (and Shelleyan) figure of the first edition. Perhaps it is Victor who renders the substitution, mindful of Walton's commitment to "enterprise," a word that, starting with the first sentence of the novel (1831:I:L1:1), he uses six times in his initial letters to his sister (see also 1831:I:L1:5, 1831:I:L2:1, 1831:I:L2:3 twice, and 1831:I:L4:20). (A context in Milton's Paradise Lost is noted in the latter.) Admittedly, it requires some stretching of the imagination and the text to force a Satanic context upon Henry Clerval: it may well be that by 1831 the original contextual referents for Mary Shelley have diminished or have been replaced by new emphases, in this case that of masculine heroism—the ardour so repetitiously invoked by her male protagonists.