The Season of the Drifter is expanding on a long-running Destiny 2 story and bringing back one of Destiny 1's most notorious guns: Thorn. The Exotic hand cannon was the scourge of the Crucible thanks to its poisonous bullets that do extra damage to players over time, making it great for racking up kills (some might even call them "cheap" kills). The gun is back in Destiny 2, provided you complete the lengthy Exotic weapon quest to get it. First, though, you need to find the start.
Watch the video above to see where you need to go to find the item you need to start the Thorn quest, but be warned: you're probably spoiling another quest line by going to get it. It may well be part of the allegiance quest offered by the Drifter, and that means you're probably skipping to the end--and might be glitching it out. You can get more details from our written guide.
You'll want to head to Trostland in the EDZ to get started. From there, head north into the Salt Mines and follow the tunnel through until you reach the elevator. Beside it is a teleporter that will take you back outside, where you can follow the path up to a camp site that was previously used by Shin Malphur.
Once you find the Melted Hunk of Metal item, you can use it to start the quest by talking to Banshee-44.