Lernaean Hydra
The large and prominent tendon of the gastrocnemius, soleus, and plantaris muscles of the calf is called the "tendo achilleus" or Achilles tendon. This is commonly associated with the site of Achilles' death wound. Tendons are avascular, so such an injury is unlikely to be fatal; however, the myth has the arrow poisoned with the blood of the Lernaean Hydra.