Lesser Invocation; 3rd
You can create an area of shadow (as the darkness spell) that is filled with bats (as the bat swarm, page 237 of the Monster Manual, except the swarm fills every square occupied by the darkness).
The hungry darkness is stationary. You are immune to the attacks of your own hungry darkness, but you are still subject to the effect of the darkness. The hungry darkness remains as long as you concentrate on it (like concentrating on a spell), plus 2 rounds thereafter. If the bat swarm is destroyed, the darkness disappears as well.
Source: Complete Arcane
Level: Brd 2, Clr 2, Sor/Wiz 2
Components: V, M/DF
Casting Time: 1 standard action
Target: Object touched
Duration: 10 min./level (D)
Saving Throw: None
Spell Resistance: No
This spell causes an object to radiate shadowy illumination out to a 20-foot radius. All creatures in the area gain concealment (20% miss chance). Even creatures that can normally see in such conditions (such as with darkvision or low-light vision) have the miss chance in an area shrouded in magical darkness. Normal lights (torches, candles, lanterns, and so forth) are incapable of brightening the area, as are light spells of lower level (such as light or dancing lights). Higher level light spells (such as daylight) are not affected by darkness.
If darkness is cast on a small object that is then placed inside or under a lightproof covering, the spell’s effect is blocked until the covering is removed.
Darkness counters or dispels any light spell of equal or lower spell level.
Arcane Material Components: A bit of bat fur and either a drop of pitch or a piece of coal.
Source: Player's Handbook