Thunderhead

Thunderheads are flesh-eating reptiles related to dragons and wyverns that almost never land and are most often met during thunderstorms. The leathery body is black, showing deep blue highlights on the rare occasions sunlight catches it, and the swept-back bat wings are soft velvety black. Its narrow, stretched head ends in a long, toothed beak, with slitted eyes of electric blue. The two legs look thin but are very strong, each splayed foot bearing three toes and an opposable thumb, all armed with wicked claws.

They mostly hunt other flyers, and their eyesight is so sharp they can spot something sparrow-sized from thousands of feet up. Their favorite move is to dive and snatch smaller prey; a hit with an attack roll of 16 or more means the claws have closed on the victim, who then takes claw damage automatically every round after. It can haul off a pair of tiny or small creatures, one in each foot, or one creature as big as a light war horse.

Against foes too large or too quick to grab, it slashes with its talons and breathes a stroke of lightning, 60 feet long and 5 feet across, for 5d6 (save vs. breath weapon for half). It can breathe once every three rounds.

Storms drive thunderheads into a frenzy. While a storm rages, they gain double Hit Dice and double hit points, along with THAC0 and experience value to match (use the figures in parentheses). Thus empowered, they swoop low and strike at whatever moves, opening with lightning and then trying to snatch their victims.

Thunderheads soar and hunt high among the clouds, eating, sleeping and even mating on the wing. They are not social, but strong rising air currents that ease soaring can attract several to one spot, and such places turn very dangerous when storms build.

They hunt every kind of flyer, from birds and bats to giant insects and even airborne humans, and during storms a frenzied one tries to catch and devour anything it sees. Sages argue over why their strength doubles. Most think the creature simply goes berserk, fighting savagely and ignoring wounds that would normally cripple it. Others hold that it actually feeds its life force from the charged air inside storm clouds.

About the only time one lands willingly is when a female briefly touches down to lay eggs. Nests are always in storm-prone country, on a sheer, sunny cliff reachable only by air, where she lays 1d4+1 eggs. Their mottled brown or gray shells are so thick that they pass for stones. The eggs hatch in about 14 weeks while the parents stay near to drive off intruders, and the shells are so tough that the young must blast free with their own lightning. Parents feed the hatchlings for about a month as they triple in size and weight. When the first storm builds, the young fall into the frenzy their parents know, launch themselves into it and begin hunting on their own by instinct.