After weeks of searching, countless theories and plenty of awesome discoveries, The First Firewall was finally revealed to be a limited time event.
If you’ve found the four fusion rifles and turned them into the gunsmith, then if you go to earth you’ll see a new mission called The First Firewall. This mission is believed to be the next step to unlocking the infamous Sleeper Simulant, though you might want to do it as quickly as possible.
According to a tweet Bungie made earlier today, it seems The First Firewall is only available for today or at least a limited time. The tweet also mentioned it will frequently return, much like the Black Spindle, but only time will tell. This has also lead to speculation that the next steps are also timed, though odds are only The First Firewall is timed, but if you want this gun you might as well do it as quickly as possible.