>Aura Break cancels the effects of the abilities Fairy Aura and Dark Aura.
>Aura Break is the signature ability of Zygarde. Similarly, the abilities it reverses are also signature abilities of legendary Pokémon from Pokémon X&Y: Xerneas and Yveltal.
It actually makes these two auras not work. It lasts until Zygarde dies, or until Zygarde switches out. If you meant Double and Triple Battles, it will cancel out both Fairy and Dark Aura, until Zygarde dies or switches.
You cannot stack up Fairy and Dark Aura together.