The level is pretty straight-forward, and it can be finished without going into the tunnels. However, it is a required level, as it is blocking the way to get to most of the levels in the Shadowlands.
The name of the level probably comes from its main inhabitants, Poison Slugs. Sleeping Slugs can also be seen underground in secluded places (the only other level they are found in is The Perilous Pit). Notoriously, no stone houses such as those in Border Village can be seen in this level (even though they are depicted in the main map thumbnail of the level). If the level name and the presence of sleeping Slugs imply that this is really is a Slug Village, it would mean that Slugs live in tunnels and underground, and that the houses on Border Village were built or used by other beings.
In this level, a total of 33,800 points can be collected. That means 2 Shikadi Sodas, 13 Three-Tooth Gums, 4 Shikkers Candy Bars, 10 Jawbreakers, 2 Doughnuts and 3 Ice Cream Cones (200 + 2,600 + 2,000 + 10,000 + 4,000 + 15,000 = 33,800). There are no less than 73 drops here, but no Lifewater Flask.
See also List of Keen 4 levels.