From Destinypedia, the Destiny wiki
The Queenbreakers were formerly the Fallen bodyguards of Mara Sov. After the Cybele Uprising, the shattered remains of the House of Wolves were given a choice; accept Mara Sov as their new Kell, or be sent to the Prison of Elders. The first to swear allegience was Saviks, Queenbreaker. These Fallen were given the privilege of serving the Queen directly beside her throne. 
Upon learning that their former Kell Skolas had escaped the Prison of Elders, the Fallen attempted to assassinate Mara Sov, but failed, as they were intercepted by the Royal Awoken Guard. Those that escaped were branded as traitors and had bounties placed on their heads. The Queenbreakers left behind their Wire Rifles, which were kept as prizes known as the Queenbreakers' Bow.
In Destiny 2, their Servitors can be seen working with the House of Dusk in Trostland, European Dead Zone. After the discovery of their escape, The Spider issued bounties on their heads, and were swiftly destroyed by the Guardians.