Original Airdate: 01/10/04
Skeletor and his Evil Warriors scatter for cover as King Hiss transforms Snake Mountain with the Medallion of Serpos, causing the snake wrapped around it to come to life and sprout two extra heads, as the mountain itself is the binding place of the mighty snake god Serpos. Under Hiss's instructions, Serpos heads for the Royal Palace of Eternia. He-Man and the Masters try to stop it, but Serpos is too powerful and breaks through them.
At the palace, the people are evacuated and the Royal Guard fire upon Serpos. Serpos breathes fire and burns parts of the palace to the ground. He-Man tries to stop him, but is knocked back so hard that he changes back into Prince Adam and loses his sword. The Sorceress calls for Zodak to come and help. King Hiss takes Serpos to Castle Grayskull to consume the power of the Elders, the very ones that long ago trapped it in stone, which led to the formation of Snake Mountain. Zodak brings Prince Adam his sword, and he transforms back into He-Man.
The Snake Men tie up King Randor and the other Masters, but Kobra Khan falls for a trick of the King's, and the small group manages to fight back. Zodak goes after King Hiss. Their final battle sees Zodak avenging his brother by hypnotizing King Hiss's other heads on his arms and around his body and making them bite the main head off of King Hiss's shoulders. The King writhes in pain, but is still sure that Serpos will soon restore him. He-Man struggles against Serpos outside Castle Grayskull until his sword splits down the middle, revealing a blade that can cut off the heads of Serpos. With two heads gone, Serpos is weak enough to be finished off.
The Elders emerge from Castle Grayskull and once again expel Serpos back to the Dark Hemisphere and turn him into stone again, trapping him as Snake Mountain. Zodak and He-Man bring the Snake Men the carcass of King Hiss. Realizing that their leader is gone and that the battle is lost, the Snake Men retreat. King Randor thanks He-Man for saving Eternia again. He-Man extends the thanks to Zodak, who has finally avenged his brother.
Synopsis by Dave Newman