Timelost Fatebringer, a rarer and harder-to-get version of the regular Fatebringer. The Timelost Fatebringer is a slightly better version which can equip with the Adept Mod, a special Mod farmed from Master and Grandmaster Nightfalls.
The Fatebringer Timelost in Destiny 2 does not drop in the normal raid and can only drop in the Master Vault of Glass. In particular, after the third encounter with the Templar there is a chance for it to drop. The Templar can also drop Vision of Confluence and Armor, hence coming it all on luck.
It is not an easy task to get a god roll Timelost Fatebringer. You need a group that the Master Vault of Glass can constantly run, and then you need to pray to RNGesus to get the right rolls.