Late one night, Shadow Weaver--the Horde's Mistress of Dark Magic--travels to the Dark Pool, a dangerous part of Whispering Woods where even the Twiggets dare not venture. There, she summons an evil monster from its bottomless depths and ensnares it in her shadowy coils.
Alerted by a group of woodcutters, Bow, a leading figure of Etheria's Great Rebellion, spies as Shadow Weaver leads the monster through the Whispering Woods. Having seen enough, he rushes to alert Princess Adora.
Meanwhile, Shadow Weaver leads the beast to a Horde base set within a mountain. Unimpressed, Hordak pits himself against the monster, but is defeated. Now satisfied with Shadow Weaver's plan, Hordak sets about unleashing the giant creature on the defenseless Etherians each night.
Later, She-Ra and Bow lead a group of Etherian men against the monster, though the Horde base's defenses prove too much for them. Worried, She-Ra summons her brother--He-man--from distant Eternia, and he, atop Battle-Cat, joins the fray quickly.
When even the combined might of He-Man and She-Ra fails to stop Shadow Weaver's monster, Kowl points out that the creature only emerges at night, and that the sun may be the key to its defeat.
She-Ra and Bow lure the monster farther and farther away from its lair, leaving it with no place to hide when the sun rises. As the monster begins to fade, Shadow Weaver appears and vows to simply conjure another monster from the Dark Pool. However, He-Man and the woodcutters have thwarted her plan by clearing away the overgrown trees that kept the Dark Pool in shadows.
As He-Man and Battle-Cat return to Eternia--giving proper credit to Kowl for his role in defeating Shadow Weaver's monster--She-Ra informs Madame Razz and the Twiggets that the body of water shall henceforth be called the Golden Pool.