Dark Dragon Balls are a set of dark red Dragon Balls with an black colored star. Uniquely they individually possess the ability to merge with evil entities to power them up, along with their ability to grant a wish when gathered.
In the Super Dragon Ball Heroes: Dark Demon Realm Mission! manga, after their creation by a Time Breaker Namekian, Towa aims to collect all of the Dark Dragon Balls so that Mechikabura can use them to wish for youth. However they scatter through space and time before they can be used and so the Time Breakers head to collect them, coming into conflict with the Time Patrol along the way.
One attaches to Frieza, during his battle with Goku on Namek, greatly empowering him. However he loses it when he is defeated - by Future Trunks in the Heroes opening, or by Xeno Goku and Namek Goku in the manga. However, when Xeno Frieza re-appears in the present time he possess the Dark Dragon Ball once more.