The Perfect Paradox, you should know the origins of this time traveling shotgun but if you don’t here is the gist. You created this shotgun for a guy named Saint-14, but you did it in the past before you were revived. Now in the Curse of Osiris story you find Saint-14 dead and he leaves you his(your) shotgun that you created somehow in the past, but your character has never seen this shotgun before.
Now on to the POSSIBLE SPOILERS
Ikora is making a Vex portal in the Tower (very bad idea) that can travel to multiple timelines to destroy the Vex known as the Undying Mind, because it left copies of itself throughout space and time and we need to find and destroy all possible Undying Minds.
Well now we have Saint-14’s shotgun and we are going to though multiple timelines and you know what? Nothing is confirmed but on the IMDB page for Destiny 2 there is a voice actor listed for whom?
Saint-14 Mic drop Boom sounds
I originally heard this theory from Byf’s Raid lore talk