According to Pindar, a goddess attempted to imitate the sound of two of these beings crying by inventing the aulos flute. Two drops of blood from these beings were gifted to either Erichthonius or Asclepius for use as a panacea. The death of one of these beings spilled blood that mixed with sand to create the viper that killed the Argonaut Mopsus and created a warrior (10[1])named (10[1])for being born with a golden sword. Ceto (10[1])mothered two immortal examples (-5[1])of these beings named Stheno (10[2])and Euryale. (10[2]-5[1])The head (10[1])of the only mortal one of these sisters (10[2])is placed (10[1])on the aegis by Athena after Chrysaor (10[1])and Pegasus are born from her beheading by Perseus. For 10 points, what snake-haired sisters from Greek myth include Medusa? ■END■ (10[1])