Ancient space weapon
A weapon of Ancient origin, constructed by the Velonans. The Ancient Orlin, who sympathized with the Velonans' quest to destroy the Goa'uld, decided to give them the plans to develop the technology that would ultimately eliminate the threat.
Once the Goa'uld were defeated, to Orlin's horror, the inhabitants of Velona began to use the weapon in conquest of other worlds. The Ancients, in return, destroyed the entire civilization and made Orlin live in seclusion on the dead planet for many years.
SG-1 found Velona and the potential for the weapon, and General George Hammond ordered SG-16 to return to analyze and possibly use the device. With this being a possibility, Orlin terminated the device by carrying the naquadah reactor, in his Ancient form, clear from Samantha Carter and SG-16 (after the Ancients' favor in him returned).
Ascension - Carter discovers a powerful weapon amid the ruins of a civilization that was not technologically advanced enough to create it.