According to Musa, there is a cave system called the Pandemonium Cave , a cave underground the Golden Auditorium where the sprites "live", which is filled with crystals. The sprites were mischievous creatures, whose screech can break a hundred glasses.
“Once upon a time, evil sprites were trapped in an elaborate system of caves. And every night, they try to escape.”
These creatures looks like large rats/mice/opossums with pangolin-like brown scales on their backs and forearms and reddish brown acorn-patterned hats. They have prehensile hands, long tails and dark brown eyes. Their pale cream skin is covered with yellow warts and their screeches are like those of mice that suggests they they might like living in dirty places.
In "The Golden Auditorium", Selina summons Pandemonium Sprites via Legendarium to "drown" the Winx with their screech. However, Musa and Tecna find out that they must use music against them and earn their Bloomix powers to return them into their cave.