Diablo serves as Maleficent's raven familiar and as a henchman to the Villain League.
When Maleficent's Goons fail to find Princess Aurora, due to the fact that they were looking for a baby for sixteen years, Maleficent entrusts the task to Diablo, instucting him to look for a beautiful maiden around 16. The sneaky bird is able to locate Aurora in a woodcutter's cottage in the forest, when he sees the magic from the fairies' wands coming out of the chimney. Later, when the fairies and Prince Philip are escaping from Maleficent's castle, Diablo is turned to stone by Merryweather.
Role in the series
It mostly serves a spy to Maleficent and Mirage, serving as their eye in the sky alongside Fagin when he's not playing the role of Big Red to Ratigan.