Failsafe is the vendor in Destiny 2 that deals with Nessus rep. It is located on Nessus near the Exodus Black landing zone. You gain access to Failsafe after doing the main missions on Nessus.
When trying to grind out Reputation for Nessus Engrams it is wise to obtain and use a Ghost that will reward you with additional Nessus Tokens upon discovering other Nessus Tokens.
Failsafe accepts Nessus Tokens, Microphasic Datalattice and Quantized Datalattice in exchange for reputation points. 20 Tokens will be required for a full level of Reputation. It will take about 100 Datalattice or 20 Quantized Datalattice for 1 full level of Reputation. Once you have handed in 20 tokens, 100 Microphasic Datalattice, 20 Quantized Datalattice or any combination of the three you can collect your Faction Reward which will show in its menu as a Legendary Engram. You can get one or more of the following items from each engram you collect from Failsafe:
- Faction Helmet (Class Specific)
- Faction Gauntlets (Class Specific)
- Faction Chest Armor (Class Specific)
- Faction Leg Armor (Class Specific)
- Faction Class Item (Class Specific)
- Nessus Pursuit Shader
- Nessus Mirage Shader
- Faction Auto Rifle: Uriel’s Gift
- Faction Pulse Rifle: Agenda 5
- Faction Rocket Launcher: Mos Epoch III
- Faction Scout Rifle: Seven-Six-Five
- Faction Sidearm: Last Hope
- Faction Sniper Rifle: Shepherd’s Watch
- Faction Submachine Gun: Out of Options
- Legendary Shards
- Misc armor pieces and weapons in a shifting lootpool
You can check the exact stats of the items or what is currently in the shifting lootpool by pressing or on the Faction Reward Engram while speaking to Failsafe.