Hydras are a pre-war species of giant, serpentine monsters, found living in Equestria's wilderness. Most notably one was living in Froggy Bottom Bog.
Hydras are large carnivores, found living in swampy or boggy locales. They can grow to be massive, easily towering over their prey. One of these creatures was encountered by Twilight Sparkle and her friends Pinkie Pie, Fluttershy, Applejack and Spike.
Hydras have four heads, each head thinks independently and has a mouth large enough to eat an alicorn. Hydra can breath out poisonous fog and are powerful enough to engage multiple alicorns simultaneously. At least one resides in the Everfree Forest, although with the cleansing/burning by Red Eye, it (they) began to move elsewhere.
For Hydra, the chemical/drug, see Medicines.
Appearances in other Stories
A hydra was shown living in the Hoofington area, beneath a factory close to Flankfurt. This Hydra was baited and fed using drug addicts captured by the dealers/producers. The Hydra would be baited with drug addicts, suspeneded in a cage above them, until one of it's heads rose up to try and eat the ponies in the cage. The drug dealers would then use a large syringe to drain taint filled material from the Hydra's head/mouth.
The material would then be used to produce the drug, Hydra. The drug has regenerative properties, able to heal up grievous injuries almost instantly.
Blackjack shut down the drug dealers operation and rescued the drug addicts, blowing up the factory they were operating out of. The factory was a pre-war fireworks factory which exploded and presumably buried and killed the Hydra living there. The chem Hydra contains Taint, and was believed to be the cause of Blackjacks failing health, since she had abused the substance to stay alive on multiple occasions. Blackjack has fought foes who were doped up with Hydra and nearly impossible to stop, due to the regeneration rate.
Hydras have a large body with a long tail to help balance them as the move and two short yet powerful legs. They have four heads, each perched on a long serpentine neck. Hydras also have green eyes, their bodies are covered in dull orange scales and bright orange spines on their heads.
Hydras are carnivorous creatures, they have four heads that act independently, making them hard to predict in battles. Each head is large enough to swallow an alicorn, the heads can also breath out clouds of poisonous fog. Hydras can breath underwater for extended times, if their presence in swampy locales is any indication. They may also be long lived as the Hydra in Evefree was close to where Twilight and her freinds encountered one, two hundred years ago.
They can breath poisonous fog to dibilitate and weaken their prey. Their necks are extrmely flexible, allowing them to stretch out and lunge at prey. They can be remarkably quick for creatures of their size.