You can find the Twilight Triumph the General section of Season of the Witch menu. The problem is that the Triumph’s objectives are “???,” “?????,” and “???????.” If you want to get the all-black Memento to add to your crafted weapons, you’ll need to unravel this mystery first.
In this Destiny 2 guide, we’ll show you how to unlock the “Twilight” Triumph and complete its mystery objectives.
Complete Fallen S.A.B.E.R. wearing the Clovis Bray mask (???)
To complete the “???” objective, you’ll need to unlock the Clovis Bray mask, which simply requires you to progress Eva’s Festival of the Lost tutorial quest. Follow the steps and then equip the Clovis mask to your Masquerader’s Helm.
With the Clovis mask on, open the map for the Cosmodrome, select the Fallen S.A.B.E.R. Strike from the map, and complete it.
Get 100 kills on Neomuna wearing the Nimbus mask (?????)
To start on the “?????” step, you’ll need to use the Nimbus mask. To get it, focus one of the new Eerie Engrams, which you can get from Haunted Lost Sectors. Once you have one, talk to Eva and open her focusing menu. Select any option under the Focused Decoding section to complete the Event Card Challenge and claim the mask.
Equip the Nimbus mask to your Masquerader’s Helm and go kill 100 enemies on Neomuna.
Finish 25 enemies in Legend Haunted Lost Sectors wearing the Tormentor mask (???????)
This last objective is a big pain in the ass, and will take you longer than all of the other objectives combined, multiplied by a few times. Consider grabbing some friends to speed up the process. If you need more help, follow Skarrow9’s video above.
To start on the “???????” step, you’ll first need to acquire the new Tormentor mask. To do this, you’ll need to defeat 100 Headless Ones in Haunted Lost Sectors and claim the Heads Will Roll Challenge. With a max of 15 per run (which requires a bit of coordination, so you’re likely to get around 12 in a group with randoms), you’re looking at at least seven runs, which should take you an hour or two. Unfortunately, this challenge is currently bugged and is only awarding progress when you defeat Headless Ones in Legend Haunted Lost Sectors, which are more difficult and take more time.
Once you’ve slogged through all the Haunted Lost Sectors and killed the appropriate number of Headless Ones, you’ll be able to claim the Tormentor mask. Equip it to your Masquerader's Helm and jump back into Legend Haunted Lost Sectors. Wearing the Tormentor mask, you’ll need to use Finishers on 25 enemies in Legend Haunted Lost Sectors.
Once you’ve completed all three of these objectives, you’ll earn the Lost Memento. To activate it, place it on any crafted weapon at The Enclave and then level that weapon up. Eventually you’ll be able to equip the exclusive all-black shader and the Headless Horror weapon title.
It’s currently unclear how to get more Lost Mementos.