I was playing Patrol on the Moon about 15 minutes ago (right around the restart, actually) and all of a sudden, in the bottom left, the text "The Minions of Crota have started a ritual" popped up. Shortly after, another message, "The Blades of Crota have invaded this world" popped up and within a minute I was fighting a gold-tinted Hive Knight called "The Blade of Crota". Upon killing him, he dropped a sword exactly like Crota's. I picked it up and had some fun with it, until a growing green electric energy destroyed it about a minute or two after I took it. I moved from Anchor of Light to the Hellmouth, where it happened again.
Is this something to do with the new raid/update? If there's anything you have to do with the sword, you have to do it fast, because it gets destroyed quickly.
Edit: I have reports from other Guardians that it's happening on Earth (this was in The Divide), and perhaps other worlds.