Some of Robert Plant's lyrics in this song were inspired by the work of J.R.R. Tolkien, author of The Lord of The Rings. The references are to the adventures of the Hobbit, Frodo Baggins, as he goes to "the darkest depths of Mordor" and encounters "Gollum and the evil one." Plant later admitted in an audio documentary that he was embarrassed by the Tolkien references, as they don't make all that much sense - a fair maiden wouldn't be found in Mordor, and Gollum would want nothing to do with her anyway, since his only concern is the precious ring.
This is one of Led Zeppelin's most enduring songs, but they never performed it live from start to finish while the band was active. It was in their set when Zeppelin reunited for a one-off concert at the O2 Arena in London on December 10, 2007. John Bonham's son Jason filled in on drums at that show.
What John Bonham played as percussion to supplement his drums on this song is not clear.
The clip Led Zeppelin — Ramble On can be downloaded for free and without registration.