BX Monsters A to Z: Bat

 Bats, from the Basic Set, are found in either normal or giant form in the D&D world. Giant bats, at least in my early campaigns, were fairly common hazards of dungeons and after-dark encounters. Normal bats, on the other hand, were sadly underappreciated.

Both sorts of bats have an AC of 6, probably representing agility and maneuverability. Both also are considered to be effectively blind as far as normal sight is concerned (real-world bats run the gamut from nearly blind to acute vision, depending on the species.) Normal ones have a single hit point each, while their giant cousins have a quite robust 2 HD. Both are skittish about combat, having a morale score of 6 in common, with normal bats needing to check morale every round or flee.

Giant bats, apart from their natural ability to fly, are fairly mundane in combat, attacking for 1-4 points of damage, which makes them potentially dangerous but not too likely to one-shot most first-level adventurers. They're explicitly carnivorous (no giant fruit bats, apparently); I would imagine their diet normally consists of normal rodents, lizards, amphibians, and the larger sorts of non-giant insects and spiders. The description says they may attack a party if extremely hungry, but otherwise probably don't have a lot of  motivation to risk their hides against sword and spell. 

Five percent of giant bat encounters, though, are giant vampire bats, which on a successful attack force a saving throw vs. paralysis; if failed the victim falls unconscious, allowing the bat to feed on its blood. A character who dies from such blood draining must save vs. spells or rise as an undead creature, possibly a vampire. This is, so far as I recall, the only instance of a posthumous saving throw in classic D&D. (Feel free to correct me if I'm wrong about that.) This strongly implies a magical or supernatural nature to this strain of giant bat.

Normal bats almost seem like a waste of an encounter, but consider that when started they may swarm around characters, causing confusion in the form of a -2 penalty to attack and making spell casting impossible. Though it isn't mentioned in the text, I might make characters holding light sources save vs. paralysis to avoid dropping light sources when first swarmed by bats, too. The bats by themselves are barely a nuisance; there would hardly be any point to even gaming out a combat with them; a brief description of the encounter would surely suffice. Where they'd really become relevant is in conjunction with a group of more dangerous creatures. They could function as a combat wild card -- which PCs and/or monsters will they swarm in any given round? They could also be purposefully used by intelligent dungeon-dwellers. Imagine, for example, a clan of goblins who live in a bat-infested cave and have learned to smear themselves with some bat-repelling herb or ointment, making them immune to being swarmed, while intruders are not. Short or low-to-the-ground creatures might also be less likely to be swarmed, especially when there are taller humans and elves to draw the attention of flying bats.

What might I change about bats? Not a lot. While 2 HD is pretty tough for a creature with long delicate bones and membranous wings, I'm not too fussed about it in the game. I'd probably bump up the normal bats' flying movement rate from 120'(40') to 180'(60') because I've been in the presence of bats, and I can tell you for absolute certain I couldn't outrun them at a full sprint, much less match their flight speed at a normal walk. Given the limited combat capabilities of normal bats and the rarity with which they're even used in games, it's probably not a big deal, but on the other hand, it's not a big deal to make the change either.