I think the most exciting thing the Traveler has done was scold Rhulk through a ghost. There has to be more to the Traveler then being just a set piece at the Tower.
It's archenemy is closing in...does the Traveler have a battle plan? It obviously can speak through ghosts...so why doesn't it more often? At the very least why hasn't the Speaker's Mask been repaired and utilized by someone. I'm sure Ikora could pull it off.
I hear Zavala going on about the Traveler constantly but it doesn't seem to be a participant in the story.
Come on Bungie, can the Traveler do something that proves that it's in this fight with us? Something unmistakable.
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The Traveler is essentially a moon sized mcguffin that can be used as deus ex machina or general plot device when needed. There is more to our magical moon golf ball in the lore but I feel very little of that lore translates into the game itself. Bungie probably has more planned out for the Traveler in the coming expansions where it will finally be fleshed out, but for now Traveler is essentially apart of the game skybox and little else.