ORIGINALLY, Blood Bowl included only two chaos teams - the Chaos team itself, and a Chaos Dwarf team. However, over time a number of experiments were attempted with adding new rosters or changing the style of play. One of the Living Rulebooks experimented with the concept of chaos teams based upon each of the four Chaos Gods. However, only one team survived that period of experimentation - and that was the team based upon Nurgle, Lord of Sickness and Decay (Chaotic Entropy, by any other name.) As such, Nurgle remains the only chaos team specifically dedicated to one member of the Chaos Pantheon (the allegiance of Chaos Dwarf teams to Hashut has never been implicitly stated, and Chaos Dwarf teams have been mentioned in fluff in as worshippers of more than one of the Chaos Gods.)
The basic story is that the team that would become "Nurgle's Rotters" was trapped on a ship somewhere in the icey waters off Norsca, and that the team swore an oath to Nurgle if he would deliver them from their predicament. Nurgle responded by infecting them all with Nurgle's Rot and showing them the way home. Since that time, the number of Nurgle teams has grown on the professional Bloodbowl circuit. It's worth noting, however, that the first mention of a Nurgle based team predates this bit of fluff. The "Subterranean Slimeballs" are mentioned in 2nd Edition as being a team dedicated to Nurgle. No further information is given on their roster or lineup.
The Nurgle team, as it might be expected, is all about plague. The players are essentially "Nurgle-esque" parodies of the players on a standard Chaos roster. While the theme makes for a different type of play for a Chaos player and those used to playing against Chaos teams, the Nurgle roster is often classiified as an Advanced Team.
0-4 Nurgle Warriors
0-1 Beast of Nurgle
Play Style and Tactics Nurgle Teams are essentially playing with an ultra-specialized version of the Chaos roster. Their Beastmen (Pestigors) and Chaos Warriors (Nurgle Warriors) are both more expensive than their equivalents in a Chaos roster; however, their basic players - the Rotters - are some of the least expensive players in the game and are generally viewed as expendable. The team benefits from Regeneration, but conversely its Rotters suffers from Decay, meaning that many players have a potentially brief lifespan. On the other hand, Nurgle's Rot gives the team the potential to recruit "new" teammates when it kills players from other teams, which mitigates the cost of finding new players somewhat.
The Nurgle team is generally considered to be slower and less mobile than the standard Chaos roster. There is much debate about whether the roster is an improvement over the former; many Bloodbowl veterans have argued that the Nurgle roster can do very effective things defensively, but they would also point out that the team is quite defficient in the scoring department (more so than the standard Chaos roster), which makes it unlikely to win many games. Coach, host of the BBtactics site, notes that the Nurgle roster should really be avoided by new players, pointing out that it lacks ball handling and blocking skills, and suffers from expensive rerolls.
The most famous Nurgle team is probably Nurgle's Rotters, the subject of the current Nurgle themed boxed set available from Games Workshop.
At the time of this writing, Games Workshop was still selling the official boxed set, based upon Nurgle's Rotters, via direct order. Several alternative Nurgle players can be acquired from a number of sources, however. As with many teams, the Fantasy Football Store is a good place to start.