Repel Vermin

(Player's Handbook v.3.5, p. 271)

Level: Ranger 3, Bard 4, Cleric 4, Druid 4, Vigilante 4, Blighter 4, Urban Druid 4,
Components: V, S, DF,
Casting Time: 1 standard action
Range: 10 ft.
Area: 10-ft.-radius emanation centered on you
Duration: 10 min./level (D)
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.