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 and a new holiday past time for the denizens of Nulndon...
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/Hanz
"Hey, Hans, the sewers are talking again. Mind tossing a few grenades down there?"
Hans and his keen eared companion are the unlikely heroes of Nuln and their timely inconvenience absolutely squashed several incursions of Skaven attacks. This method of handling Skaven dweller attacks spurred a new holiday in Nulndon, celebrating the successes and triumphs of the city by summarily tossing grenades down the sewers. The Grenade and Sewer Gate becomes the symbol of the Guild of Urban Hygiene and Sanitation.