Level: Bard 4, Cleric 4, Druid 4, Ranger 3
Components: V, S, DF
Casting Time: 1 standard action
Range: 10 ft.
Area: 10-ft.-radius emanation centered on you
Duration: 10 minutes/level
Saving Throw: None or Will negates; see text
Spell Resistance: Yes
An invisible barrier holds back vermin. A vermin with Hit Dice of less than one-third your level cannot penetrate the barrier. A vermin with Hit Dice of one-third your level or more can penetrate the barrier if it succeeds on a Will save. Even so, crossing the barrier deals the vermin 2d6 points of damage, and pressing against the barrier causes pain, which deters most vermin.
Source: Player’s Handbook (version 3.5), page 271.