Bonebat (CR 2)

Medium Undead
Alignment: Always neutral evil
Initiative: +1 (Dex); Senses: darkvision 60 ft., see invisibility, Listen +5, and Spot +5

AC: 13 (+1 Dex, +2 natural), touch 11, flat-footed 12
Hit Dice: 4d12 (26 hp); DR: 5/bludgeoning
Fort +1, Ref +2, Will +4
Speed: 10 ft., fly 50 ft. (average)
Space: 5 ft./5 ft.
Base Attack +2; Grapple +3
Attack: Bite +3 melee
Full Attack: Bite +3 melee
Damage: Bite 1d6+1 plus paralysis 1d4+1 rnds
Special Attacks/Actions: Paralysis
Abilities: Str 12, Dex 13, Con -, Int 6, Wis 10, Cha 14
Special Qualities: Weapon immunities, undead,
Feats: Alertness; Flyby Attack
Skills: Hide +5, Listen +5, Move Silently +5, and Spot +5
Advancement: -
Climate/Terrain: Any land and underground
Organization: Flock (2-6)
Treasure: None

Source: Monster Compendium: Monsters of Faerûn

Bonebats are undead bats that serve as messengers, guardians, and battle allies to evil clerics and wizards and to powerful undead (such as liches and vampires). They appear as skeletal giant bats with a 5-foot wingspan and dark, empty eye sockets.

Bonebats have darkvision with a range of 120 feet.