Leshrak Not-Swim served a lifetime under Captain Skretch Half-dead. When that lifetime was over he, and the rest of the crew, found themselves transformed into something more. Something permanent. Like all Skaven, Leshrak had spent his life worshipping at the alter of the Great Horned Rat. He became the Chaplin of the pirate ship Skabrus in the Dreadfleet (after the previous Chaplin "accidently" drank some holy water), but found that few would heed his calls to worship. Once the ship went to shore, he set off, finding other preachers in the undead town square (more of a pyramid, really). Various builders and other susceptible fools heard their message, and they began to plan. Just like a Skaven should.