There's a Lost Sector up North that, to my knowledge, nobody is investigating. The area in the map provided matches what we see in the Strike perfectly, and the tower and door are perfectly described by Cayde. It's not a Story Mission or a Lost Sector. There IS an actual Lost Sector in/around the Tree though. We should be working to see if we can get in there instead. Comment with more information if you find out and I will add instructions later.