https://www.polygon.com/2018/10/17/17991218/destiny-2-thunderlord-cosmodrome-festival-of-the-lost

For weeks, there has been a rumor in the Destiny community that the Thunderlord exotic machine gun will be returning as part of Destiny 2’s Festival of the Lost event, the series’ Halloween stand-in. After the recent Destiny 2 patch, players have been able to search through the game’s new data to find evidence of the exotic’s return.

As of patch 2.0.4, there is a new classified heavy exotic in the Collections tab — one that nobody has or knows how to get. One of Thunderlord’s original perks, Feeding Frenzy, has also appeared in the game’s database and is currently unattached to any weapon. This is similar to what happened when players first discovered Black Spindle’s signature perks — the weapon is called Whisper of the Worm in Destiny 2 — in the game’s database.