Flying Under the Influence

The other night my player group encountered some vampires flying overhead in bat form. A quick thinking magic user cast a Slow spell on them. On the assumption that the vampires would be unable to flap their wings fast enough to keep flying, I had them drop into some bushes. The PCs repeatedly cast Slow on them and managed to beat the crap out of them, forcing them into gaseous form. Since then I've been reconsidering how I handled this situation...

I don't think the proper effects of Slow on flying creatures would be quite so simple. Flying creatures can control their speed and altitude by varying how hard and fast they flap their wings. Takeoffs, steep climbs and high-speed flying require maximum effort, or close to it, whereas level cruising flight takes less, and at times a winged creature can glide motionlessly. A creature flying at its normal speed is exerting the same effort as a creature walking.

If this type of situation ever comes up again I'm going to rule that flying at cruising speed takes half maximum effort. A Slow spell would cut this speed in half, but the creature could still maintain normal speed by trying as hard as possible, just as a slowed person who tries to run can achieve walking speed. Slowed flying creatures would be unable to take off or climb, and they would be unable to fly level if they carried any weight besides their own bodies.

Slow does not affect gravity, so a slowed creature making a downward diving attack should be able to dive at normal speed. Even though the creature would attack at a penalty because of impaired motor function, the time it took to plunge toward its victim would be normal, and any effects that depend on the physics of mass and falling velocity would be normal.

What if you used a Wand of Paralyzation on a flying creature? As a kid I saw a television show in which a large bird had snatched up an infant. To avoid killing the infant, a wise hunter carefully shot the bird through the brain. This made all the bird's muscles clench up, and it spiraled slowly to the ground in a gentle glide. This might not have worked in real life but it made for a good plot. For gaming purposes I think the same principle should apply to a creature paralyzed in flight. It would simply glide to an uncontrolled crash landing, or wherever the prevailing air currents took it. For example, updrafts near a mountainside or the rising hot air above a volcano might make it gain altitude. Whirlwinds or rough weather could destabilize it and send it tumbling to the ground. The creature would be at the mercy of the elements.