I could believe that Forerunner shield worlds like Onyx could have been the genesis of the idea for the traveler. There are at least two Grimoire cards that make references to Dyson Sphere's (which are at the core of the shield worlds of Halo lore, as seen in Halo Wars and Halo 4, as well as Ghosts of Onyx and the Karen Traviss trilogy). Ghost Fragment: Ghosts [spoiler]"The powers in charge have carved up all of the worlds, and maybe a brown dwarf or two for good measure. With that rubble, they fashioned a topologically creative enclosure, a twisting of space and time sealed behind doors that admit only those who know the magic words. The bones of a hundred planets have been cut smooth and laid out like a floor, a polished and lovely floor creating vast living spaces. A floor bigger than ten thousand worlds, catching the fierce glory of the seven suns. For light, for food. For beauty. And nothing escapes. Not heat, not gravity. Not even the faintest proud sound."[/spoiler] Ghost Fragment: Mysteries 2 [spoiler]"A world painted around the interior like a stranger Earth everted and glued inside itself but I don't believe this one it's too much like a metaphor."[/spoiler] I've also seen related theories that the Ghosts are like the Monitors from Halo in that they are the digitized "souls" of the Traveler's inhabitants. Where things go from there I don't know, but I find the story possibilities that these concepts open up to be rather intriguing.