The Sturm is an Exotic Weapon in Destiny 2.
It’s obtained from completing the questline “Failsafe” on Nessus after the story. The quest is started in the Exodus Black region in the north-east corner of Nessus. You have to talk to Rahool in the Tower hub and decrypt 5 legendary and 1 exotic engrams. This quest is going to take a while to complete, it’s recommended you start it as soon as you finish the story and reached level 20. After decrypting the engrams you get a few more follow up quests in which you have to kill some enemies and talk to another NPC at the farm.
Failsafe quest location:
Exotic Name: Sturm
Type: Kinetic Primary Weapon, Hand Cannon
Item Description: These ancient ceremonial pistols can be dated back to the early Golden Age. A faded inscription reads, “To Sigrun, from Victor”.
Special Ability: Accomplice — Kills fill Energy weapon mags.
Acquired by: Complete Failsafe Quest on Nessus after the story.
This weapon is especially powerful when combined with the ‘Drang’ secondary weapon. When killing enemies with one weapon it reloads the other automatically!