Definition: Amphicyon, in Greek mythology, refers to a giant dragon who lives in the River Styx, an ancient river located deep under Greece's mainland. This dragon had three heads: two large ones at its back and one small, projecting from its side. When it came to feast time, it would eat both the fish and the frogs. The dragon was originally thought to be made of stone but turned out to be human-like when he ate the frogs. This mythological creature inspired countless tales and myths around the world.