Just shy of a week ago Bungie gave us our first glimpse at Destiny. During the 15 odd minutes of game play Joe picked up the "Thunderlord", which is an exotic weapon. Joe then proceeded to look at how he weapon could be upgraded. As I was reading on the forums many people seemed disappointed that the weapon had a very linear upgrade path, opposed to an upgrade tree. This had me slightly disappointed as well, so I came up with a reason as to why the upgrade path was so linear: the gun is exotic. I think it may be possible that exotic guns can only be upgrade a certain way, while normal guns will allow for more diverse paths to be taken. The reason I think this is because exotic guns already have an established history to them, whilst a normal gun that you bought in The Last City has only began its journey and its history needs to be written. All exotic weapons will be identical, but your favourite and most used weapon will be the only one in the whole solar system.