Short answer: I think yes. If you watch the reveal trailer, I immediately recognized that the scene showing Osiris was within the Vault of Glass, particularly the Templar area (that ramp behind him when he slides to cover gave it away for me). There's also a slight appearance of an Oracle behind one of the pillars in that same scene. The most interesting thing people are talking about is that the bullets and Guardians within those scenes are frozen. My hypothesis is that Osiris was probably there while we were confronting the Oracles and the Templar. Skipping over the whole timey-wimey stuff, Osiris probably intervened on another chronological plane while we were fighting the Vex on our own. Osiris was most likely assisting getting rid of possible reinforcements, thus easing up that portion of the Raid. For those wondering if Osiris was responsible for the Aegis (shield) appearing in the activity, most likely not. Kabr, Pahanin, and Praedyth ventured into the Vault at one point long before we did; and ultimately failed to stop the Vex. Praedyth got endlessly trapped within the Vex network, Pahanin escaped, and Kabr was the last one in the Vault. For future Guardians (us), he offered his Light to become the Aegis, which became our weapon against the Templar and Atheon. Thus, Osiris most likely didn't have a role (unless he somehow found Kabr long before). There is the possibility that the scene Osiris was shown in was when Kabr's fireteam descended into the Vault. They failed at eliminating the Oracles, as the Grimoire depicted their difficulty with fathoming how they worked; and because a Templar isn't shown and a portion of an Oracle is, it could be that Osiris intervened then and not when we descended. There is also a lot of other potential for this DLC to expand on various lore pieces within the universe: Brother Vance, Praedyth, Saint-14, and Eris Morn. As for the Exo Stranger - I know, I know. Luke Smith said that Bungie was satisfied with the conclusion of the Stranger. BUT, that COULD mean that her story has a happy ending after vanilla Destiny, but her story could POTENTIALLY BEGIN during the Curse of Osiris. Maybe Bungie's doing the whole "from the beginning, you know the end" thing like they pitched in Halo: Reach. Probably not going to happen, but one could hope for the future, right? The [b]Black Heart[/b] has been pretty neglected post-TBD's launch. We can assume that it's another form of the Darkness, or corrupted Light as I like to put it (I have a whole theory on this), and that the Vex supposedly worship it because it's uncomputable even by the Vex. But why was it necessary for the Black Garden? And if it was, why does the Garden still exist? Will we ever kill the Undying Mind? Will the Vex ever thank us for saving their butts from the Taken during the Paradox mission? According to Praedyth, apparently not. As it was etched onto the No Time to Explain pulse rifle, "Soon."