PYRAIKHMES (or Pyraechmes) was a king of the island of Euboia who made war on Boiotia. He was vanquished by Herakles, who had him torn in two by his own horses.
Elements of this myth recur in the stories of Diomedes of Thrake and Erginos of Orkhomenos.
Pseudo-Plutarch, Greek and Roman Parallel Stories 7 (trans. Babbitt) (Greek historian C2nd A.D.) :
"Pyraikhmes, king of the Euboians, was at war with the Boiotians. Herakles, while still a youth, vanquished him. He tied Pyraikhmes to colts, tore his body into two parts, and cast it forth unburied. The place is called 'Colts of Pyraikhmes.' It is situated beside the river Herakleios, and it gives forth a sound of neighing when horses drink of it. So in the third book of Concerning Rivers."
- Plutarch, Parallel Stories - Greek History C1st-2nd A.D.