Nulndon
After the destruction of Marienburg, Carrotburg and Altdorf, Nuln became the greatest city of the Empire. However, once again it was threatened by Skaven, who sought to overrun it through the sewers.
Use of grenades to combat them led to massive upgrades to the sewer system including Gromril grates, leading to greater levels of hygiene and overall growth of the city...
The Nulndon meme originated in an October 2014 Warhammer Fantasy General thread on /tg/. Originally instigated by a conversation beginning in an evaluation of the industries remaining in the Empire after the attacks of Nurgle's forces during The End Times event, a series of jokes reminded the fa/tg/uys why Nuln is the only Empire city most people remember.
The thread chain begins here: [1]
Hans
"Hey, Hans, the sewers are talking again. Mind throwing a few grenades down there?"