Anti-Ori weapon
Designed by the Ancient Merlin to destroy ascended beings, specifically the Ori. It is an energy transfer device that channels energy into the dimension occupied by ascended beings. In theory, the weapon can destroy ascended beings by interference -- as two standing waves cancelling out one another.
Believing the weapon to be linked to Merlin's amulet, SG-1 follow the clues left by Merlin and complete hazardous tasks set by Morgan Le Fay, finally meeting the dying Ancient.
anti-Ori weapon parts in assembler, from The Quest, Part 2 Before he dies, Merlin downloads his memory into Daniel Jackson, using a device similar to the Ancient repository of knowledge. Daniel then uses the Ancient assembler to create the weapon's components.Before he can complete the weapon Daniel is captured by Adria the Orici, and is turned into a Prior.
It falls upon Vala to complete the assembly of the weapon which, it turns out, is also known as the Sangraal, using instructions left by Daniel. The weapon is then used to try and eliminate the Ori.
KEY EPISODES
Arthur's Mantle - Once on the other side, Daniel reads the display on Merlin's computer, explaining the weapon he was building and the location to where he left it.
Camelot - Kvasir theorizes about how Merlin's weapon works, while SG-1 gains a vital new clue about where to find it.
The Quest, Part 1 - SG-1 discovers the planet where Merlin likely hid the Sangraal, but must get past a series of obstacles set by Morgan Le Fay before they can reach it.
The Quest, Part 2 - As the Ori forces close in, SG-1 race to complete the weapon.
The Shroud - The newly activated weapon is sent through the Ori's super-gate.
Stargate: The Ark of Truth - SG-1 learns from Adria that the anti-Ori weapon did indeed work, wiping out the evil ascended beings.