People are saying that obtaining that Exotic pulse rifle (the SIVA one) will be somehow connected to getting all of the clusters. I dunno if that's true or not, but if it is then I'm well on my way, with all 26 of the ones that are currently available. The most annoying ones were easily the one on top of Felwinter Peak and Fallen 3.0. Hopefully when the raid comes out tomorrow the other 4 will be available.