Hydra

The Lernean hydra, shortened to simply Hydra, is a serpentine monster in Greek mythology that resided in lake Lerna which is the source of Lernean in its name. The Hydra has from 3 to 9 heads and was virtually unbeatable given it;s powerful claws, which could slice through trees with ease, and its many heads which could attack from multiple directions. On top of that it could spew toxic fumes and had toxic blood

The attribute it is most famous for was its ability to sprout two heads when one was severed. Though this skill was countered when Heracles and his nephew Iolaus used a torch to cauterize the wound after Heracles decapitated one of its heads.

It was the offspring of Typhon and Echidna and is the sibling of Orthrus, Cerberus and Chimera.

Image source: https://www.thenewdealer.org/news/2016/02/06/the-hydra-of-new-york-city/