From AllMusic.com:
After Physical Graffiti came out in 1975 to unanimous critical and commercial raves, Jimmy Page and Robert Plant traveled to North Africa to gather ideas for a follow-up. Unfortunately, Plant broke his ankle in a car accident, which essentially squelched Led Zeppelin's momentum as well as their seven-year winning streak. The band decided to reassemble and quickly write and record what would turn out to be Presence. Hence, meticulous attention to detail was not an option, as the band reverted to a no-frills approach not heard since their first album. "Achilles Last Stand" is the most ambitious song on Presence, the only one that resembles the layered masterpieces from Physical Graffiti. The title was a nod to Plant's broken ankle as well as the mystic locale which inspired the lyrics. The "guitar army" approach that Page had successfully employed on "Stairway to Heaven," "The Song Remains the Same," and "Ten Years Gone" is the most distinctive feature of this song as well, which features dozens of guitar overlays. The rhythm of the song is very galloping and influential, without which Heart's "Barracuda," and Iron Maiden's entire oeuvre, could not have possibly existed. In particular, John Bonham's drum track is his most devastating ever, combining a breakneck pace with startling finesse. Plant's trip to the Atlas Mountains of Morocco was the impetus for the lyric "...where the mighty arms of Atlas hold the heavens from the earth...," but the song is probably vaguely autobiographical and not unlike Plant's common Zeppelin motif of the endless quest, an idea he employed almost as much as his more famous lemon-squeezing theme. "Achilles" was played on the 1977 North American Tour at an even faster clip than the record and seemed quite ramshackle and under-rehearsed on most nights as a result. Tracks like this one are Led Zeppelin's true legacy, for they are influential yet never duplicated, much like the band itself.