Clan Merkit
Last stands can often be inspiring to people; sadly, for Skaven, the last stand of Clan Merkit was anything but inspiring. The Southlands had long been home to Skaven, so when Clan Pestilens made a comeback and established a home there, most of the other clans didn't think much of it. But when the Council of Thirteen refused to welcome Lord Nurglitch, the leader of Pestilens, into their number, things got ugly quickly.
Chemical warfare annihilated most of the strongholds stationed in the Southlands. Against all odds, Clan Merkit held strong, being one of the "major clans". Deciding to speed things along, Pestilens poured cauldrons' worth of filth and warpstone through the caverns linking into Merkit's stronghold. The entire clan (save for Lord Merkit and his honor guard) was destroyed within a few hours. A shameful disgrace had fallen on these Skaven, and Lord Merkit... well, nobody ever heard from him again!