The hydra (ὕδρα)
is a polycephalic reptile native to Lake Lerna in Greece. The number
of heads common to this species has been variously reported as five,
seven, nine, or a hundred (the last known sighting of a hydra
occurred more than three milennia ago, by a certain Heracles (a
notable wildlife enthusiast of the day) so any knowledge we have of
this creature has suffered from the Chinese whispers of time).
Nonetheless, all accounts agree that the hydra regrows two heads for
each one cut off, and has poisonous breath and blood.
Due to the overcompensatory nature of its response to trauma, Nassim
Taleb has elected the hydra as the symbolic beast of antifragility.
It roams the sands of Extremistan indifferent to danger, impervious
to harm. The one known Black Swan for the hydra is cauterisation, so
it seems the hydra has no natural predators. Yet it is not even sure
that the hydra will survive the Blank Swan of my writing.