Their agent, Xûr, sells powerful items for an unusual currency and is able to travel freely between the Tower and the Reef.1 It is unknown whether his presence is permitted.
When the Queen of the Reef's crows trespassed into the Nine's territory she gave them Skolas as a gift.2 For reasons unknown, the Nine released Skolas and restored his Ketch, instigating the rebirth of the House of Wolves.3