The biggest mystery of Destiny: The Taken King has finally come to light. The Sleeper Simulant questline is now accessible, so if you've been deciphering hidden codes, searching for secret rooms, and coming up empty handed, your search is nearly over. If you haven't gotten the quest yet, here's how we think you kick it off.
To get started, you will need to have collected four legendary Dark Age fusion rifle relics that have names similar to DAVLIN-RAS8711-FR002. These can randomly drop from enemies in any event in the Cosmodrome, Moon, Venus, and Mars areas. Once you get them, turn them in to the Gunsmith in the Tower.
When you do this, a mission will appear on the Director in the Cosmodrome called The First Firewall. This requires you to enter Rasputin's bunker once again and kill all of the Taken enemies within. Once you defeat the Taken Knight boss, you will receive an item called the Curious Transceiver. Inspect the Curious Transceiver in your inventory, located in the mission items section and you will be prompted to input four codes using two rows of symbols. The codes are as follows, (the number 1 indicates the top row and 2 is the bottom row). Thanks, Reddit!
1 2 1 1 2 2 2 1 2
1 2 1 1 2 2 1 1
1 2 2 2 1 2 2 2 1 1
1 2 1 2 1 2 1 1
When you've entered the codes correctly, another mission will appear in the Cosmodrome called Shadow Call. This mission requires you to scale the tower from the Cayde's Stash quest in under 4 minutes. On the way up you will need to kill every Taken Wizard on the way. Do this and you will get an item called the IKELOS Fusion Core.
From there, you'll need to assemble the IKELOS Fusion Core. To get the Heavy Power Coupling, dismantle a legendary heavy weapon. The Ionized Shell Harmonics portion can be found by playing through The Archive mission on Venus. To get the Plasma Confinement Control Modules, you will need to defend three different Warsats in the Cosmodrome, Moon, and Mars public events. Destinypublicevents.com has handy event timers for public events on each planet, which makes finding the Warsats much easier.
After you've completed the requirements for each of the IKELOS Fusion Core nodes, go into your inventory, inspect the item, and select each node to complete them. When that is done, head over to the Tower and turn the IKELOS Fusion Core in to the Gunsmith.
Annnnd, now you wait. After the Daily reset at 2am PT / 10am UK time, return to the Gunsmith and he'll give you the final part of the quest. It's a level 42 version of the Fallen Saber Strike (yes, yes) with the Epic modifier. However, this Strike - despite being Nightfall difficulty, and carrying a recommended Light Level of 280 - DOES have matchmaking. So you don't need to form a fireteam before heading in.
Complete the quest to earn the Sleeper Simulant frame. Now, finally, head back to the Gunsmith and he will give you the finished weapon... Or is it finished? The description on it says "Midnight Exigent: Status = still in progress". So maybe this isn't the gun's final form.