Cinema "really emerged as a reference point for how we arranged out music [on The Mantle]," said guitarist Don Anderson. He suggested that the band was "thinking in images and how sound might express those images". Taking a more mellow tone than Agalloch's first full-length, Pale Folklore, The Mantle still contains heavy electric guitarriffs as well as acoustic guitar portions. Anderson pointed to the influence of neofolk music, particularly Death in June, as the impetus for using a strummed acoustic guitar in a darker musical context. Present as well are long and melancholic double bass sequences, such as on the track "I Am the Wooden Doors". A critical influence upon Agalloch during this time period was Godspeed You! Black Emperor, with Anderson remarking:
Godspeed, in particular, was the major influence. Their approach to the guitar seemed aligned with black metal. The guitar was no longer a purely riff-based instrument, but provided an ambiguous atmosphere through tremolo-picking either large chords or single melodic lines.
On March 28, 2005, Profound Lore Records released a double LP version of The Mantle on grey-colored vinyl. Limited to 500 copies, it also featured exclusive cover artwork.