Have you noticed some Destiny 2 NPCs refer to the Drifter as Dredgen? Ever seen Guardians with the same title or wonder what it has to do with Thorn? It turns out there is a fully-fledged story behind all this but we never got to experience it.
If you happened to walk around the Tower and saw some Guardians brandishing the Dredgen title, you may have asked yourself what it actually means. Some characters also refer to the Drifter as Dredgen but he is not the source of the name or the title.
It all started with a Titan named Rezyl Azzir, who was the hero of both Faction Wars and the subsequent Fallen invasion, wielding signature weapons Inferno and Rose. The man was a fabled hero of The Last City before it was even built and now he is the most hated Guardian to walk the face of the Earth.
This is because he later became disillusioned with the Guardians' mission to protect innocents and cursed by Xyor, a Hive Wizard. It is implied the curse had something to do with the corrupted version of Rose, now known as Thorn.
He adopted the name Dredgen Yor and started killing Guardians and Lightless alike. He eventually met his end at the hands of Shin Malphur, the first Guardian who was not originally dead and the one who created Golden Gun in that exact confrontation.
Following Dredgen Yor's demise, some Guardians started obsessing over his connection to the Darkness and tried following in his footsteps. In order to flush out and hunt down these Guardians, Shin Malphur created Shadows of Yor group and temporarily took the name Dredgen Vale. Similarly, everyone who joined took a new name, with the first one always being "Dredgen".
In other words, the title Dredgen is now a title and marker of one's affiliation, much like Darth is to the Sith Lords in Star Wars universe. Employing the name or title also paints a target on one's head since Shin Malphur is relentlessly hunting them down in order to prevent another menace like Dredgen Yor from happening.
Drifter was briefly known as Dredgen Hope but pulled out of the order. He met Shin Malphur who question him but managed to divert the Hunter's attention to another Dredgen, known as Callum Sol or Dredgen Cull.