|The Heretic Geth dreadnaught explodes just as Shepard escapes.|
Trying to reclaim Rannoch, their homeworld, the Quarian fleet is engaged in battle with a Geth fleet that includes a Geth dreadnaught they are trying to destroy. Turns out that the Geth virus in Mass Effect 2 didn’t save the Heretic Geth and bring them back to the Geth collective. The heretic Geth are now fighting for the “old machines” and are opposed by the Geth who are losing their fight against them.
Shepard uses the Normandy’s stealth systems to fly through the fight and dock with the dreadnaught. Their mission is to disable its systems so the Quarians can destroy it. Overall this is fun mission. After boarding the dreadnaught you fight your way through the ship to turn off its turrets and other capabilities. Of note is that each time the big guns fire a surge of energy goes through the passage you are in. If this hits you it wipes out your shields making you easy prey for the Heretics defending the passage. So remember to take cover when you see the power surge coming.
|Legion captured and connected to the dreadnaught network.|
Towards the end you discover that the Heretic Geth have imprisoned Legion and are using him and the Geth collective as a large server to operate the dreadnaught, communicate and other miscellaneous tasks.
You free Legion and he explains the Geth/Heretic Geth situation to you. Legion then helps you to disable the dreadnaught and escape. Seems that the Quarian Admiral leading the attack choses to attack the dreadnaught rather than waiting for you to escape. You need lay smack down on him for that!
This sets the stage for another encounter on the Quarian home world of Rannoch where Shepard ultimately decides the fate of the two races and Tali and Legion. Like The Highlander "there can only be one."