From Press Release:
Cayde-6 has paid the ultimate price. Now, the hunt is on for the man responsible, Uldren Sov. Avenge Cayde in Destiny’s most transformative experience yet, and track down Uldren and his Barons. It will take every Titan, Warlock, and Hunter to storm the Reef and put Uldren in the ground.
The adventure to avenge Cayde begins on September 4.