hydras

noun
  1. 1

    Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.

  2. 2

    A dragon-like creature with many heads and the ability to regrow them when maimed.

  3. 3

    A complex, multifarious problem or situation that cannot be solved easily and rapidly.

Source: https://en.wiktionary.org/wiki/hydra, https://en.wiktionary.org/wiki/hydras