Zero Hour
From Destinypedia, the Destiny wiki
Zero Hour is a secret quest found on Earth when the player has the Falen Transponder and has activated all 6 of its nodes. A completion of this quest awards the player with the Outbreak Perfected Exotic Pulse rifle. This quest can be accessed via the Earth directory or by interacting with Mithrax, the Forsaken in The Farm basement after the player has the Falen Transponder and has activated all 6 of its nodes.
Heroic version
After the completion of the quest, a heroic version will be available via an option after selecting the Zero Hour mission on the Earth directory. When the player completes the heroic version of Zero Hour for the first time, they will be awarded the Outbreak Perfected Exotic catalyst. After the player completes the heroic version of Zero Hour for the first time, further completions will award 100 SIVA Nanites which count towards completing the Outbreak Perfected Exotic catalyst.