She-Ra: Princess of Power: Season 1, Episode 14

1 - 14: He Ain't Heavy

Shadow Weaver and Grizzlor steal the magic mirror from an old wizard. Hordak then uses that mirror to snatch prince Adam from Eternia and blackmail princess Adora to come and surrender. But when Adora comes as She-Ra and frees Adam who finds a spot to turn into He-Man, Hordak tries to use the mirror once again to capture king Randor. But by the second time he uses it, the moons are not aligned and the mirror turns into black hole-like entity sucking everything in and threatening everyone in vicinity.