Was just doing patrol on the forgotten shores when a message appeared: The minions of Crota started a ritual.
A minute later it said: The Blades of Crota have invaded this world.
Any information on that? Maybe thats how you get the sword during patrol?
Edit:
Guys I found it. There was a Knight roaming around called Blade of Crota. Killed him, got the sword
http://i61.tinypic.com/2zgcc9v.jpg
-
If you stick around mothyards you should find it.