Final answer:
The god Hermes, or Mercury in Roman mythology, placed his wand between two fighting serpents to test his wand's power, resulting in the caduceus symbol.
Step-by-step explanation:
The god who placed his wand between two fighting serpents to test his wand power was Hermes (known as Mercury in Roman mythology). Hermes is often depicted with the caduceus, a staff entwined by two serpents, which is a symbol associated with commerce and negotiation, traits that Hermes governed as a deity in Greek mythology. The caduceus is sometimes mistakenly used as a symbol of medicine, conflated with the Rod of Asclepius, which has only one serpent and is a true symbol of the medical profession.