This spell can be cast upon an enemy unit in line of sight. If that unit is within 24" then every model in the unit must pass an Initiative test, and those that fail the test must then take an armour save. If a model passes its armour save, its weight will drag it down into the rotting slurry - remove that model from play. This spell has no effect on units with the Fly, Amphibious or Ethereal special rules.