Dagger of Xian is the item on which whole story of Tomb Raider 2 revole around.It`s make second apperance in Tomb Raider 3 (as an easter egg) and now it`s make third apperance here in TR:AOD. Here is the way to get it:

1:Start the level "Aquatic Research Area".

2:Go through the level until Lara change her clothes.

3:Now go back to the main hall.

4:Go toward the underwater area where you pulled the first lever but don`t dive into the water.

5:Enter the door there and keep walking until you reache the end of the room.

6:Dive into the water.

7:Swim under the water and through the big opened door.

8:Don`t swim through the open door in front of you.

9:Turn left and swim toward the pipes.

10:After you reached to the pipes "Roll" Lara.

11:You will see a stair and on it`s left side you will see a wall with lights on it.

12:Swim toward that wall and use it.

13:Lara will perform the moonsault like move on it and the wall will be pushed inside.

14:Go through the opened wall and swim toward the surface.

15:Climb the ladder.

16:Now push the block(wall) in front of you.

17:Until it push no-more.

18:Look at your left.

19:*SURPRISE* You will now see a glass box with "Dagger of Xian" in it and with two spot light spotting on it.

NOTE:You must change Lara clothes first otherwise she will not push the wall.