I haven't been to the light house (or played ToO for that matter, it doesn't really interest me) , but if the secret room is what you're talking about, I think the desk and those books are Osiris's. I don't think the Speaker is that awesome to travel to Mercury XD. Maybe we'll see him do something cool in the latter DLCs.

The paper work and little trinkets and sculptures are all similar... That's what I meant. It's one thing to see it on YouTube, another to view it yourself at your own pace. And, btw... there are two closed off rooms in the lighthouse that are 'blocked' by some shield. I wonder what's there....???

I'll try to get into Lighthouse and see what you're talking about, but in the meantime I'll just add it to the post. Happy hunting for more :). I think the two rooms are reserved for more rewards, there is still that exotic ship and sparrow, maybe they'll be given after the TTK dlc hits for going flawless.