Lost City tablet
Stone tablet found by Daniel Jackson in a hidden chamber on Abydos. The tablet is written in a dialect of the Ancients and tells of the Lost City of the Ancients -- promising a cache of advanced weapons and technology left behind when the species ascended to a higher plane of existence.
Full Circle - SG-1 finds a tablet on Abydos, and Jackson risks everything to make sure it gets back to Earth safely, promising to help the team find the Lost City.
Fallen - The tablet is duplicated, slightly altered, and placed on another world as a lure for Anubis, in order to draw him to the planet Vis Uban -- where SG-1 attacks his mothership, destroying his new super-weapon.