Asuran satellite weapon
An Asuran built weapon which fires an immensely powerful beam. It is essentially a stripped down spaceship, with a hyperdrive engine, shield generator, navigation system and power source. At one end of the satellite is a Stargate and, once dialed and connected, the beam is fired through the wormhole from the Asuran homeworld of Asuras.
During a council of war on Atlantis Rodney McKay suggests that the weapon may be powered by a black hole or an unlimited number of Z.P.M.s. The beam takes over supplying power to the defensive shield making the satellite practically invulnerable to attack. It also powers the Stargate, which overrides the 38-minute rule on wormhole connection. In addition the gate's operation means that no nearby gate can used to dial out, effectively trapping the people on Atlantis.
First Strike - In response to an attack on their homeworld, the Asurans send their satellite weapon to attack Atlantis.