At two kilometers long, Sovereign is the largest known dreadnought in the Mass Effect galaxy. The massive fleet was the flagship to the rogue Spectre Saren Arterius.
Sovereign has a conversation with Commander Shepard in the first Mass Effect game. You would think that the main enemy in the game would make death threats and/or mock the its opposers, but Sovereign, surprisingly, was wildly inappropriate (he asked Shepard to touch his "ding ding dong") in this fan mashup:
The lyrics for that song originated from Gunther, a Swedish artist who became famous from his "Ding Dong Song" in 2004: