you may not have an idea as to how Destiny might pull off something like that, but I certainly had an inkling just now! Ok, Here is how Destiny's "big secret thing" could play out. You play the majority of the game, about 80% of it to be precise. Then, subtly, you start to catch wind of something secret and deadly (the big secret thing) and you start to find reports of sightings and strange occurrences. Then, second to last mission, The entire mission is devoted to finding something, some kind of big Foreshadowing device that pretty almost guarantees that something secret is stirring out there. Then, Destiny ends with absolutely 0 encounters with "the big secret thing" HOWEVER when the Sequel to Destiny comes out, The entire first half of the game is completely silent about the "big secret thing", then, halfway through, the eerie feeling starts to set in and then BAM, you finally encounter the thing that you have been hearing about since Destiny 1! Then you spend the remainder of the game dealing with it and combating it (if its an entity that you can combat). that would be the best way, in my opinion, to have another "Flood" moment in Destiny. The storytelling would be incredible and it certainly has the room for creativity in Delivery. But Destiny does need a "Flood moment". It needs to be subtle, and it needs to be wonderful. Just like the Reveal of the Flood, it needs to be unexpected.